Septuagint (LXX):  kai Boos anebe (3SAAI) epi ten pulen kai ekathisen (3SAAI) ekei kai idou o agchisteutes pareporeueto (3SIMI) on eipen Boos kai eipen (3SAAI) pros auton Boos ekklinas kathison (2SAAM)  ode kruphie kai exeklinen (3SAAI) kai ekathisen (3SAAI) 

Septuagint (LXX):  kai elaben (AAI) Boos deka andras apo ton presbuteron tes poleos kai eipen kathisate (2PAAM) ode kai ekathisan (3PAAI)

AND HE TOOK TEN MEN OF THE ELDERS OF THE CITY AND SAID SIT DOWN HERE SO THEY SAT DOWN:  (Ex 18:21,22; 21:8; Dt 29:10; 31:28; 1Ki 21:8; Pr 31:23; La 5:14; Acts 6:12):

He took (03947) (laqach) conveys the primary meaning to grasp or take hold of. Boaz took hold of 10 men from the elders to serve as witnesses, although only two or three witnesses were needed for judicial proceedings (cf. Dt 17:6).

Centuries later 10 became the number necessary for a Jewish marriage benediction or a quorum for a synagogue meeting. For an official prayer meeting in modern Judaism 10 men are required. The point is that this was a time in history when few written records were kept, and attestation by a number of witnesses was the most efficient way to be certain that a transaction was made legally secure.

Elders (02205) is related to the Hebrew word (zaqan) for beard.  The elders functioned in both a political and judicial role. They would hear disputes, weigh the evidence and render a decision. As alluded to earlier, in the case of Boaz, they were functioning primarily as witnesses rather than as jurors. Elders would serve as judges as elsewhere in the OT we see that they were to deal with criminal cases (Dt 21:18, 19, 20, 21), and with family matters, such as levirate marriage (Dt. 25:7, 8, 9).

The Hebrew word is translated with the Greek (Septuagint -LXX) noun presbuteros which was used to refer to men who were older or more senior and is transliterated into English as “presbyter”, a word that was used for leaders in the Jewish community and eventually becoming a term used to describe those who were members of the Jewish ruling council, the  Sanhedrin. In regard to the Greek word presbuteros, the secular practice was for older men with seniority to serve as ambassadors to other states and as advisors within the Greek political community or in the management of public affairs. So these were men of "ripe age" and experience to whom was committed the direction and government of individual churches. It should be emphasized that in the context of its Biblical use the concept of elder had less to do with age per se than with the quality of one's spiritual character (reputation is what others think about you but character is what those most intimately associated know is really true about you) and possession of the ability to teach. Simply being older, including even being older in the faith, does not by itself qualify a man for leadership in the church.

Matthew Henry comments on the character of Boaz which was indicated by his willingness to call public witnesses writing that

Honest intentions dread not a public cognizance.

Sit down - A key phrase in Ru 4:1,2 (4x). Boaz commanded (Hebrew verb in form of a command) them to sit, and they responded to Boaz, a "pillar" (cp 1Ki 7:21) in the community, a man of excellence and one not given to jesting or wasting people's time.

So - Consequently. Undoubtedly the respect of the elders for Boaz's reputation prompted their response to the request of Boaz.

Septuagint (LXX):   kai eipen (3SAAI) Boos to agchistei ten merida tou agrou e estin (3SPAI) tou adelphou hemon tou Abimelech e dedotai (3SRMI) Noemin te epistrephouse (PAPFSD) ex agrou Moab 

Then - This little "time" sensitive word (see importance of expressions of time) marks a progression in the discourse (next in order of time) and emphasizes the willingness and wisdom of Boaz to wait until all the "players were in place". It would not have been prudent to speak with the nearest kinsman redeemer in the absence of witnesses. The wise man is willing to wait. The writer of proverbs records that...

he who makes haste with his feet errs. (Pr 19:2b, see also Pr19:2NLT).

Do you see a man who is hasty in his words? There is more hope for a fool than for him. (Pr 29:20, see Pr 29:20NLT)

The plans of the diligent lead surely to advantage (Good description of Boaz's plan and actions - he took no shortcuts! Do I?), but everyone who is hasty comes surely to poverty. (Pr 21:5, see also Pr 21:5NLT).

To the closest relative - The Goel or Kinsman redeemer, the man who had the first right of redemption.

Naomi...has to sell the piece of land - As a destitute widow, Naomi undoubtedly needed the money for living expenses (and this even in spite of Boaz's gracious gifts of grain). No information is given as to how she came to possess it.  This verse reveals for the first time in the story that Naomi owned the property.

Has to sell - The Hebrew is in a form of the verb (see note below) that indicates the sale was as good as done. The only thing that remained to be determined was the buyer. The property might be sold to anyone, but covenant law allowed Naomi the right to have her kinsman-redeemer buy the land back from a stranger at any time.

Fruchtenbaum writes that...

In the Hebrew text the tense ("sell") is perfect, which normally indicates completed action, and therefore it would mean that it had already been sold. But Ru 4:5 and Ru 4:9 indicate that she was in the process of selling the land, and so the perfect tense would then indicate her determination or resolve to sell the land, and thus, most translations use the present tense, which is correct...the land had not yet been sold; otherwise, it would have to be redeemed from its new owner and not from Naomi. (Fruchtenbaum, A. G. Ariel's Bible commentary: The books of Judges and Ruth. San Antonio, Tex.: Ariel Ministries)

The NET Bible notes that...

The perfect form of the verb here describes as a simple fact an action that is underway (cf. NIV, NRSV, CEV, NLT); NAB “is putting up for sale.”

The Amplified Version translates this verse as follows:

And he said to the kinsman, "Naomi, who has returned from the country of Moab, has sold the parcel of land which belonged to our brother Elimelech".

The well respected Old Testament commentary (Keil and Delitzsch) translates this verse like the Amplified...

The piece of field which belonged to our brother (i.e., our relative) Elimelech (as an hereditary family possession), Naomi has sold.

NKJV renders it as if Naomi had "sold the piece of land" which implies a transaction had taken been consummated.

Young's Literal has "a portion of the field...hath Naomi sold".

In context, Boaz tells the nearest kinsman to buy the land and so in effect to redeem it. Leviticus records that

If a fellow countryman of yours becomes so poor he has to sell part of his property, then his nearest kinsman (Goel - the kinsman redeemer) is to come and buy back what his relative has sold. (Lev 25:25)

The land would ultimately be returned at Jubilee (Lev 25:28). Since Jubilee came only every fifty years God had provided another way to redeem the land and that was through the provision of the kinsman redeemer. 

Jubilee means a joyful shout or clang of trumpets, the name of the great semi-centennial festival of the Hebrews. It lasted for a year. During this year the land was to be fallow, and the Israelites were only permitted to gather the spontaneous produce of the fields (Lev 25:11, 12). All landed property during that year reverted to its original owner (Lv 25:13-34; 27:16-24), and all who were slaves were set free (Lev 25:39-54), and all debts were remitted.

The advantages of this institution were manifold. "

1. It would prevent the accumulation of land on the part of a few to the detriment of the community at large.

2. It would render it impossible for any one to be born to absolute poverty, since every one had his hereditary land.

3. It would preclude those inequalities which are produced by extremes of riches and poverty, and which make one man domineer over another.

4. It would utterly do away with slavery.

5. It would afford a fresh opportunity to those who were reduced by adverse circumstances to begin again their career of industry in the patrimony which they had temporarily forfeited.

6. It would periodically rectify the disorders which crept into the state in the course of time, preclude the division of the people into nobles and plebeians, and preserve the theocracy inviolate." (Easton's Bible Dictionary)

Mills notes that

The English text emphasizes Naomi’s return, but the Hebrew literally reads, “The portion of the field which is our brother Elimelech’s, has been sold by Naomi who has returned from the fields of Moab.” By placing the field first in his sentence, Boaz emphasized the material aspect rather than the personal aspect of the transaction, and in so doing probably appealed to an avaricious streak in this relative. (Mills, M: Ruth : A study guide to the book of Ruth Dallas: 3E Ministries, 1999)

Our brother - Calling Elimelech our brother is the Hebrew word ('ah) that means simply "a relative" or "kinsman", in this case bringing out the fact both Boaz and the nearer goel were related to Elimelech.

Piece of land which belonged to Elimelech - Remember that Ruth was married to Mahlon, so at first this statement seems somewhat confusing.

Butler...

The availability of this land is another illustration of the failure of Elimelech in moving to Moab. His move to Moab was to procure gain, but all it did was produce loss. Anytime we leave the place where God wants us in order to procure gain in the world, we will end up a big loser. (Ibid)

Warren Wiersbe offers a reasonable explanation that

In the case of Ruth and Naomi, Elimelech’s property had either been sold or was under some kind of mortgage, and the rights to the land had passed to Ruth’s husband Mahlon when Elimelech died. This explains why Ruth was also involved in the transaction. She was too poor, however, to redeem the land. (Wiersbe, W: Be Committed: An Old Testament Study. Ruth and Esther. Victor. 1993)

The Bible Background Commentary observes that...

Septuagint (LXX):  kago eipa  (1SAAI) apokalupso (1SFAI) to ous sou legon ktesai (2SAMM) enantion ton kathemenon (PMPMPG) kai enantion ton presbuteron tou laou mou ei agchisteueis (2SPAI) agchisteue (2SPAM) ei de me agchisteueis (2SPAI) anaggeilon (2SAAM) moi kai gnosomai(1SFMI) oti ouk estin (3SPAI) parex sou tou agchisteusai (AAN) kago eimi (1SPAI) meta se o de eipen (3SAAI) ego eimi agchisteuso  (1SFAI)

Thought to inform you - This reads more literally "I will uncover your ear", a small but significant detail. Boaz could have just said "I was going to tell you..." but the point is that Boaz did not seek to hide anything from the nearest Goel. Boaz had promised that Ruth would be "covered" with someone's wings and his first objective was to remain true to his word.

Butler...

The word "advertise" in the KJV text is translated from two Hebrew words. The first Hebrew word means to reveal, disclose, publish, remove, and uncover. The second Hebrew word means ear. The combination of the words means literally to uncover the ear (push back the hair or head covering of another so you can speak in their ear). The first Hebrew word is translated "uncover" in Ruth 3:4,7 regarding Ruth uncovering Boaz's feet at night on the threshing floor....

Much character is revealed in acknowledging our place in line. The flesh always wants the preference. It always wants to be first in line. One can see this when shopping in some store or standing in line at a cafeteria or bank or some public event. People are always crowding ahead of others in line by pushing and shoving and cheating. Boaz would not do that, however. He had high character and would stay in his place in line. It is a humbling position, but it is also a very honorable one. (Ibid)

The Greek translation (Septuagint) conveys this openness of Boaz  by using the verb apokalupto (word study) (601) (from apo = from + kalupto = cover) which means to remove the veil or covering so as to expose to full view what had previously been hidden. Apparently the nearest relative did not know that he was in fact first in line to perform the role of kinsman redeemer. Boaz could have "gotten away with it" but he was open and honest. While Boaz was surely in love with Ruth, he was still willing to trust God with the outcome (Pr 3:5, 6).

Matthew Henry comments that

Boaz might have said, “My money is as good as my kinsman's; if I have a mind to it, why may not I buy it privately, since I had the first proffer of it, and say nothing to my kinsman?” No, Boaz, though fond enough of the purchase, would not do so mean a thing as to take a bargain over another man's head that was nearer akin to it; and we are taught by his example to be not only just and honest, but fair and honorable, in all our dealings, and to do nothing which we are unwilling should see the light, but be above-board.

SAYING "BUY IT BEFORE THOSE WHO ARE SITTING HERE AND BEFORE THE ELDERS OF MY PEOPLE IF YOU WILL REDEEM IT REDEEM IT": (Ge 23:18; Jer 32:10, 11, 12)

Before those who are sitting here - This phrase emphasizes the formal nature of this transaction and as we find out later reflects not only the elders' presence but the fact that there were other Bethlehemites in attendance.

If you will redeem it, redeem it - As alluded to earlier, the Mosaic Law provided for land to stay within a family, even if it had to be sold temporarily due to poverty. The Law allowed for the seller to redeem the land themselves later if they were able (if they somehow acquired the necessary funds) or for a close relative (the goel) to redeem it. If neither of these alternatives was possible (no money or no willing Kinsman-Redeemer, the land by divine decree must still be returned to the original owner (or their posterity) in the Year of Jubilee, which as noted above "cycled" every fiftieth year. The point is that the land was not to be sold permanently because the Jews were in a sense tenants and ultimately the land belonged to God, Moses recording that...

The land, moreover, shall not be sold permanently, for the land is Mine; for you are but aliens and sojourners with Me.  (Lev 25:23)

Redeem means “to set free by paying a price.” In the case of Ruth and Naomi, Elimelech’s property had either been sold or was under some kind of mortgage, and the rights to the land had passed to Ruth’s husband Mahlon when Elimelech died. This explains why Ruth was also involved in the transaction. She was too poor, however, to redeem the land.

BUT IF NOT, TELL ME THAT I MAY KNOW FOR THERE IS NO ONE BUT YOU TO REDEEM IT AND I AM AFTER YOU AND HE SAID "I WILL REDEEM IT": (Lev 25:25, 26, 27, 28, 29)

But - Always introduces a "change of direction" and cause us to stop and ask what is the change?

I will redeem it - Not, "I will think about it", but an immediate affirmative reply. Does not his swift answer and his subsequent response make us question his motive. Does he really want to aid a poor widow or does he want to take advantage of her plight?

I - In the Hebrew sentence the "I" is emphatic so that the sentence reads something like "I, I will redeem it". The nearer kinsman-redeemer was happy add this fine parcel of land to his financial portfolio, for in that day land was especially equated with one's wealth and social status. The fact that he answers affirmatively without asking any other questions indicates that he must have reasoned that at  Naomi's age she would ever give birth to a son (who would carry on Elimelech's name and would thereby become the rightful heir to the land according to the Mosaic Law). His quick affirmation also indicates he did not know there were "strings attached" so to speak. And so few men who would be able to function as a kinsman redeemer would have passed up the opportunity that appeared to have presented itself. In other words he would look like the generous, altruistic Goel (with the esteem that surely must have come with the carrying out of such a "selfless" act) and eventually end with the parcel of land.

On the other hand, just imagine how Boaz must have felt upon hearing nearer kinsman's emphatic affirmation "I will redeem it"!  Boaz's hopes must surely have sunk, and yet there is no record that he gave evidence of the disappointment he surely must have felt inside. Boaz is quite a man of character, irregardless of the circumstances! 

Butler...

Septuagint (LXX):  kai eipen (3SAAI) Boos en hemera tou ktesasthai (AMN) se ton agron ek cheiros Noemin kai para Routh tes Moabitidos gunaikos tou tethnekotos kai auten ktesasthai se dei hoste anastesai to onoma tou tethnekotos (RAPMSG) epi tes kleronomias autou 

Then - This time phrase marks a key transition point in this exchange, for now Boaz (still with integrity) "plays his trump card", informing the nearer kinsman of his duty to redeem the posterity of Elimelech, if he wishes redeem the property of Elimelech. The nearer kinsman isn’t just dealing with aged and childless Naomi, but is also dealing with Ruth who is young and fully capable of giving birth to a son who would inherit the land.

Henry Morris adds that

The right of a kinsman-redeemer to redeem the property of a dead relative, thereby preventing it from passing outside the family, is set forth in Leviticus 25:25-34. These events described in the book of Ruth indicate that this right of property redemption was also directly linked to the responsibility of raising up children to preserve "the name of the dead upon his inheritance." (Morris, Henry: Defenders Study Bible. World Publishing)

THE WIDOW OF THE DECEASED IN ORDER TO RAISE UP THE NAME OF THE DECEASED ON HIS INHERITANCE: (Ru 3:12,13; Ge 38:8; Dt 25:5,6; Mt 22:24; Lk 20:28)

Your purchase of the land from Naomi requires your marriage to Ruth so that she can have children to carry on her husband's name and to inherit the land. (TLB)

so that the field will stay in the dead man's family (TEV)

in order to maintain the name of the dead with his property  (NIV)

What Boaz stipulates appears to be related to the so-called "law of levirate marriage" (but see the note below regarding this interpretation). Moses instructed the Israelites in Deuteronomy that

"When brothers live together and one of them dies and has no son, the wife of the deceased shall not be married outside the family to a strange man. Her husband’s brother shall go in to her and take her to himself as wife and perform the duty of a husband’s brother to her. And it shall be that the first-born whom she bears shall assume the name of his dead brother, that his name may not be blotted out from Israel." (Dt 25:5,6)

When Elimelech died, the property went to Mahlon; and when Mahlon died, the property then included the widow Ruth. She was now part of the redemption responsibility, and the property would go to any son born to her to perpetuate the family line. In other words a goel was needed to buy the land and take Ruth as wife to carry on the name of Ruth's husband, Mahlon. In carrying on the name of Mahlon, the line of Elimelech would also continue.

The Bible Knowledge Commentary adds that

Apparently at the death of Elimelech the property had passed to Mahlon so Mahlon’s widow Ruth was included in the redemption responsibility. A son, to whom the property would belong, should be raised up to perpetuate the family name. (Walvoord, J. F., Zuck, R. B., et al: The Bible Knowledge Commentary. 1985. Victor).

Boaz informs the nearer goel that he had to "buy (07069) (qanah) the field" and also "acquire" (same verb qanah = "buy") Ruth! Not only did this come as a surprise to the nearer goel, but Boaz also made known Ruth's nationality “Ruth the Moabitess.” The fact that Ruth was a Moabitess may also have been a problem to him. (Both Mahlon and Chilion had married Moabite women and died!) In any event what looked like a "windfall" suddenly seemed far less attractive since the man would be required to marry Ruth (acquire the dead man’s widow) and the income derived from the land would not go directly to the redeemer’s estate. Moreover, his own estate would possibly have to be divided with Ruth’s children. With an expectant intake of breath we await his reply.  It’s worth noting that the nearer kinsman tried to protect his name and inheritance; but we don’t even know what his name was or what happened to his family!

The Wycliffe Bible Commentary says that

"Both the alienation of land and the extinction of a family were to be prevented by the law of the goel. The goel would not come into possession of the land himself, but would hold it in trust for his son by Ruth, who would inherit the name and patrimony of Mahlon (her first husband)." (Pfeiffer, C F: Wycliffe Bible Commentary. 1981. Moody)

The interpretation of this passage however does have some difficulties.

The Expositor's Bible Commentary comments that Boaz

reminded the kinsman of a condition he must satisfy to redeem the land. He must marry (qanah "buy," "acquire," "redeem") Ruth the Moabitess (Heb., "buy the field from the hand of Naomi and from Ruth") to bear children to restore the name of Elimelech to his inheritance in accordance with the levirate law (see Deut 25:5, 6). The firstborn son of their marriage would legally be Mahlon's son. It is difficult to know whether the kinsman must buy Ruth (NASB, RSV follow the Vulgate and Syr.) or buy from Ruth (with KJV, NIV, following the MT). Furthermore, this case differs from the levirate law on several counts: (1) here a more distant relative than a brother was expected to marry the widow (Ed note: “levirate” means “husband’s brother” ) (2) the kinsman removed his own shoe instead of the rejected widow doing it; and (3) apparently no disgrace was involved, as the significance of removing the shoe here was to seal a legal transaction. Boaz probably hoped to discourage the kinsman from buying the land by reminding him that the purchase of the land obligated the kinsman to marry Ruth, though he gave the kinsman every opportunity to do just that. (Gaebelein, F, Editor: Expositor's Bible Commentary OT 7 Volume Set: Books: Zondervan Publishing)

John MacArthur adds that

Both redeeming Ruth and the land would not have been required by the letter of the levirate law (Dt 25:5, 6). Perhaps this exemplified Boaz’s desire to obey the spirit of the law or maybe redemption of land and marriage had been combined by local tradition. (MacArthur, J.: The MacArthur Study Bible Nashville: Word Pub)