THEREFORE ALSO IT WAS CREDITED TO HIM AS RIGHTEOUSNESS: dio kae logisthe (3SAPI) auto eis dikaiosunen:

This verse sums up and brings to climax Paul’s argument in Romans 4:1-21 concerning Abraham’s justification by faith.

Why "therefore"? Because of Abraham's (Abram's) faith and to what has just been said of the confidence with which Abraham laid hold of God's promise...

"Then he believed in the LORD; and He reckoned it to him as righteousness." (Ge 15:6).

John MacArthur makes the point that...

It is not that faith merits salvation but that faith accepts salvation from God’s gracious hand. Through that acceptance comes the righteousness that only God can impart. (MacArthur, J: Romans 1-8. Chicago: Moody Press)

Credited (3049)  (logizomai from lógos = reason, word, account) means Christ's righteousness was reckoned or imputed to Abraham’s account

Logizomai was used in Greek business transactions as shown by the following phrases -- “put to one’s account,"  "let my revenues be placed on deposit at the storehouse",  "I now give orders generally with regard to all payments actually made or credited to the government.”

NKJV "just as David also describes the blessedness of the man to whom God imputes righteousness apart from works"

In (Ro 1:18-3:20 - see Tabular Schematic above) Paul clearly demonstrated the moral and spiritual bankruptcy of the entire human race. However, the application of the righteousness of Christ to the moral and spiritual ledger of a man's life will cause the books to "balance", providing a perfect standing before God in Christ.

Righteousness (1343) (dikaiosune) is rightness of character before God and rightness of actions before men. Both of these qualities are based on truth, which is conformity to the Word and will of God. Righteousness is the sum total of all that God is, all that God commands, all that God demands, all that God approves, and all that He Himself provides in His Son Christ Jesus, Paul explaining that the Father...

made Him who knew no sin to be sin on our behalf, that we might become the righteousness of God in Him. (2Cor 5:21)

NOW NOT FOR HIS SAKE ONLY WAS IT WRITTEN: ouk egraphe (3SAPI) de di auton monon: (Ro 15:4; 1Cor 9:10; 10:6,11; 2Ti 3:16,17)

Paul's point here is that the narrative concerning Abraham was written not merely to relate the facts concerning his history, but also to preserve the knowledge of an event which should take place in our lives as well...

"For whatever was written in earlier times (referring to the Old Testament) was written for our instruction, that through perseverance and the encouragement of the Scriptures we might have hope." (see note Romans 15:4)

All Scripture has universal application and Abraham’s experience is no exception. If Abraham was justified by faith, then all others are justified on the same basis.

This passage parallels Paul's affirmation that...

All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness that the man of God may be adequate, equipped for every good work. (See note 2 Timothy 3:16-17)

THAT IT WAS CREDITED TO HIM: hoti elogisthe (3SAPI) auto:

"It" refers to righteousness, the righteousness of our Lord Jesus Christ made available by His substitutionary sacrificial death on the Cross.

Credited (3049)  (see logizomai) is used by Paul much as was it was used in the business world to convey the idea of imputing or putting Christ's "assets" paid for at Calvary on to the destitute sinner's otherwise empty spiritual account.

Credited (logizomai) is used by Paul 19 times in (Click uses). It follows that one might have difficulty understanding this great letter if he or she does not understand the meaning and nuances of logizomai.

C H Mackintosh writes that...

Abraham was called to believe in a promise, whereas we are privileged to believe in an accomplished fact. He was called to look forward to something which was to be done; we look back on something that is done, even an accomplished redemption, attested by the fact of a risen and glorified Savior at the right hand of the majesty in the heavens. (Mackintosh, C H: The Mackintosh Treasury: Miscellaneous Writings by C. H. Mackintosh)

After answering the question from the Genesis record, he now shows that the Old Testament Scriptures are not merely a record of facts, but that they are permanently designed for the benefit of all believers (cp. Ro 15:4).

This happened two thousand years before Paul, but Paul says God did not write those words for Abraham alone. For whom were they written then? For us, today.

We look at the faith of Abraham and say, "That was extraordinary faith." Paul says it wasn't; it was ordinary faith. Anyone can exercise such faith if they want to. You can have righteousness too. You can be a friend of God, accepted before him, with worth and value in his sight -- not just once as you begin your Christian life, but every day, taking it fresh from his hand. You are forgiven of your sins, restored, every day afresh and anew -- a thousand times a day if you need it. All that Abraham had -- the promises of the world, the indwelling of the Spirit -- all are ours as well.

TO WHOM IT WILL BE CREDITED AS THOSE WHO BELIEVE IN HIM: mellei (3SPAI) logizesthai (PPN)  tois pisteuousin (PAPMPD) epi: (Ro 10:9,10; Mk 16:16; Jn 3:14-16; Acts 2:24; 13:30; Eph 1:18-20; Heb 13:20,21; 1Pet 1:21)

Credited (3049) (logizomai) from lógos = reason, word, account) means to reckon, compute, calculate, to take into account, credit or impute  to one's account, to deliberate, and to weigh.  Logizomai refers to a process of careful study or reasoning which results in the arriving at a conclusion. Logizomai conveys the idea of calculating or estimating.

Note Paul's use of the present tense which indicates this belief is habitual or continuous. It is a lifestyle of faith.

Thus belief stands in stark contrast here with "work" and those who say that "belief" is a "work" have not understood Paul's point. We can do nothing to merit being declared righteous. Yes, we believe but that is not a work of our flesh that merits God's salvation. It is analogous to a drowning man holding up his hand to the one who has reached down to save him.

"In" is literally "upon" (1909) (epi) which signifies, not merely the acceptance of a statement, but the restfulness of faith that leans upon the Person Himself (Who are you leaning on? Self or Savior? Not just the first time in salvation but everyday in every way believers need to rely on and lean on Him to be able to live the Christian life, the "Christ" life).

Now if we believe upon the God who raised Jesus from the dead and we are ready to live on the basis of his death and his life for us, we, like Abraham, are heirs of all the world. All these things are yours, Paul says. The indwelling of the Spirit is granted to us moment by moment, and day by day, all our life long. And we, like Abraham, are the friends of God.

WHO RAISED JESUS OUR LORD FROM THE DEAD: ton egeiranta (AAPMSA) Iesoun ton kurion hemon ek nekron: 

Raised (1453) (egeiro) was used literally to refer to arousing or awaking someone from sleep. Egeiro was used literally also to raise up or lift up a person either sitting or lying down. Figuratively egeiro was used to "raise up" a person from illness, thus restoring them to health. Figuratively as used here in Romans 4:24, egeiro is used to describe the bringing back of Jesus from the dead and thus raising Him or causing Him to rise. The idea of wake up from death conveyed by egeiro because sleep was used as metaphor of death for believers (there is however no "soul sleep").

Jesus (2424) (Iesous) is the Greek form of the Hebrew Jeshua (Yeshua) or Joshua, a proper name meaning "Yahweh saves" or "whose help is Jehovah".

Lord (2962) (kurios) is defined as he to whom a person or thing belongs, about which he has the power of deciding and thus over whom one is master and owner. The primary idea of kurios relates to possession of power and/or authority by the one so called. Is Jesus your Kurios?

TDNT has an excellent introductory note on kurios writing that...

Historically the concept of lordship combines the two elements of power and authority. A true realization of the unity of the two arises only in encounter with God, Who creates us with absolute power but is also the absolute Authority before which it is freedom rather than bondage to bow. In the Biblical revelation the humanity that rejects subordination to its Creator meets the One Who with the authority of God's ministering and forgiving love woos its obedience and reconstructs and reestablishes the relations of lordship. (Kittel, G., Friedrich, G., & Bromiley, G. W.  Theological Dictionary of the New Testament. Eerdmans)

From (1537) (ek) is a preposition which denotes exit or emission out of, as separation from, something with which there has been close connection, in this case from the dead.

Dead ( 3498) (nekros akin to Latin "neco, nex" from a root signifying "to disappear" - according to Thayer) defines those who have breathed their last and thus who are deceased, lifeless and no longer physically alive.

Abraham’s faith rested upon God as the One who could bring life out of natural deadness. We also believe in Him who quickens the dead, but in this case His almighty power has been already put forth in the Resurrection of Christ (1Pe 1:21 Eph 1:19, 20), the resurrection making our justification before God possible, for the Resurrection proved the efficacy of Christ’s death and demonstrates that Jesus, the living One, can make us right with God.

The Resurrection of the Lord Jesus Christ is the cornerstone of the gospel as Paul declared to the Corinthians...

Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand, by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain. For I delivered to (paradidomi - see Ro 4:25) you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried, and that He was raised on the third day according to the Scriptures, and that He appeared to Cephas, then to the twelve. After that He appeared to more than five hundred brethren at one time, most of whom remain until now, but some have fallen asleep; then He appeared to James, then to all the apostles; and last of all, as it were to one untimely born, He appeared to me also. (1Corinthians 15:1-8)

The truth of the resurrection is absolutely essential to the gospel of Jesus Christ. Without the resurrection, there is no "good news" for all men who are born (spiritually) dead in their trespasses and sins because of their birth into the lineage of Adam (see note Romans 5:12).  In light of the importance of the resurrection, Paul emphasized...

But if there is no resurrection of the dead, not even Christ has been raised; and if Christ has not been raised, then our preaching is vain, your faith also is vain. Moreover we are even found to be false witnesses of God, because we witnessed against God that He raised Christ, Whom He did not raise, if in fact the dead are not raised. For if the dead are not raised, not even Christ has been raised; and if Christ has not been raised, your faith is worthless; you are still in your sins. Then those also who have fallen asleep in Christ have perished. If we have hoped in Christ in this life only, we are of all men most to be pitied. But now Christ has been raised from the dead, the first fruits of those who are asleep. For since by a man came death, by a man also came the resurrection of the dead. For as in Adam all die, so also in Christ all shall be made alive. (1Corinthians 15:13-22)

If you have a God Who can raise the dead and Who can call into existence the things that do not exist, you are going to be a very exciting person to live with. You will never know when a thing that is spiritually dead and dull and lifeless may be touched by the grace of God and brought to life again. When something that you cannot possibly hope for -- something which does not now exist, but which will be called into existence by the God Who calls into existence the things that do not exist -- when such a thing is promised by a God like this, life is a great adventure. That is faith, when all things are yours. Do you have that kind of God? You can settle that today, even as you read this note, in your own heart and then...

when this perishable (physical earthly body) will have put on the imperishable (incorruptible body characterized by an unending existence), and this mortal (subject to death) will have put on immortality, then will come about the saying that is written,

"DEATH IS SWALLOWED UP in victory.

"O DEATH, WHERE IS YOUR VICTORY?

O DEATH, WHERE IS YOUR STING?"