THE INFAMOUS "JOHANNINE COMMA"
KJV 1Jn 5:7-8 - For there are three that bear record [in heaven, the Father, the Word, and the Holy Ghost: and these three are one] 8 And there are three that bear witness in earth.
Almost all authorities agree that the text in bold italics above in the KJV is not in the original Greek and for that reason those words are not found in most modern translation (ESV, NAS, ESV, NIV).
On a separate note related to translation, if you use the older version of the NAS (1977), be aware that the new version (1995) shifts the first clause of verse 8 (For there are three that bear witness) to verse 7. The clause that was present in the 1977 version (And it is the Spirit who bears witness, because the Spirit is the truth) is in turn shifted to the end of verse 6 in the 1995 NAS.
Hiebert explains that "The statement in verse 7 (KJV) concerning the three heavenly witnesses [in heaven, the Father, the Word, and the Holy Ghost: and these three are one] , commonly known as the Johannine Comma, is an expansion of the Greek text upon the basis of the Latin and is devoid of any reliable textual support as a true part of the original. Hodges and Farstad in the edition of The Greek New Testament According To The Majority Text, generally supportive of the Textus Receptus, rightly omit verse 7 entirely. Erasmus did not find the words in any of the Greek texts upon which he based his first two editions of his Greek New Testament, but in the third edition, in a spirit of compromise, he reluctantly included them in his text. Accordingly they were contained in the Textus Receptus upon which the translators of the King James Version based their English rendering. Because verse 7 in the King James Version is not an authentic part of the Greek text, it is here not given any interpretative treatment (The Epistles of John- An Expositional Commentary).
Marshall another respected authority on First John writes "This form of wording appears in no reputable modern version of the Bible as the actual text; most editions adopt the same practice as in the NIV of relegating the extra words to a footnote, while some (such as the RSV and NEB) totally ignore them. The words in fact occur in none of the Greek manuscripts of 1 John, except for a few late and worthless ones, and are not quoted by any early church writers, not even by those who would have joyfully seized upon this clear biblical testimony to the Trinity in their attacks on heretics; they probably owe their origin to some scribe who wrote them in the margin of his copy of 1 John; later they were erroneously regarded as part of the text. Beyond any shadow of doubt the wording of the NIV text represents what John actually wrote." (The Epistles of John - The New International Commentary on the New Testament- I. Howard Marshall)
W E Vine - The seventh verse, given in the KJV is not part of the original. No Greek manuscript earlier than the fourteenth century contains the passage. No version earlier than the fifth century in any other language contains it. (The Collected Writings of W. E. Vine)
MacDonald adds that "It always disturbs some devout Christians to learn that parts of verses 7, 8, as found in the KJV and NKJV, are actually found in only a handful of Greek manuscripts of the NT. But this does not at all affect the truth of the inspiration of the Scriptures. Some people think it is important to retain the words because they mention the three Persons of the Trinity. However, the truth of the Trinity does not depend on this passage alone, but is found in many other portions of the Scriptures… Having stated in the previous verses the Person and work of Christ, John now goes on to state the trustworthiness of our belief in Him." (Believer's Bible Commentary)
For there are three - John has only mentioned one witness up to this point, declaring that "it is the Spirit Who testifies" in 1Jn 5:6-note. He had stated that Jesus came by water and blood, but did not refer to them as witnesses at that time. These three witnesses are specifically named in the next verse (1Jn 5:8-note).
For (hoti) is a term of explanation, which always begs the question of what is the writer explaining? In this case it is not completely clear. For example, Westcott says "This clause appears to give the reason for the main proposition in 1Jn 5:5-note, that ‘Jesus is the Son of God,’ a truth briefly expressed and affirmed by His full Name, ‘Jesus Christ.’ (in 1Jn 5:6-note) A E Brooke offers a somewhat similar thought that this term of explanation explains why the "witness to the fact that Jesus is the Christ, the Son of God, is trustworthy. It fulfils the conditions of legally valid witness, as laid down in Dt. 19:15." (ICC New Testament Commentary)
Three that testify - Who are the three that testify or give witness? "the Spirit and the water and the blood" as recorded in 1Jn 5:8. To what do they testify? In context they testify to the truths concerning Jesus Christ which John has just recorded…
1Jn 5:1-note "Jesus is the Christ" (Or as rendered in 1Jn 5:1HCSB "Jesus is the Messiah")
1Jn 5:5-note "Jesus is the Son of God."
1Jn 5:6-note "This is the One who came by water and blood, Jesus Christ"
Three (5140)(treis) is the cardinal number three.
Treis - 69x in 62v translated Usage: fifty-three*(1), thirty(1), three(66), twenty-three*(1).- Mt 12:40; 13:33; 15:32; 17:4; 18:16, 20; 26:61; 27:40, 63; Mark 8:2, 31; 9:5, 31; 10:34; 14:58; 15:29; Luke 1:56; 2:46; 4:25; 9:33; 10:36; 11:5; 12:52; 13:7, 21; John 2:6, 19f; 21:11; Acts 5:7; 7:20; 9:9; 10:19; 11:11; 17:2; 19:8; 20:3; 25:1; 28:7, 11f, 15, 17; 1Cor 10:8; 13:13; 14:27, 29; 2Cor 13:1; Gal 1:18; 1 Tim 5:19; Heb 10:28; Jas 5:17; 1 John 5:7f; Rev 6:6; 8:13; 9:18; 11:9, 11; 16:13, 19; 21:13
Why does John mention three "witnesses"? While one cannot be dogmatic it would be reasonable to follow the pattern presented for human witnesses as described by Moses in Deuteronomy "A single witness shall not rise up against a man on account of any iniquity or any sin which he has committed; on the evidence of two or three witnesses a matter shall be confirmed." (Dt 19:15) A number of other Scriptural passages describe the number of witnesses required to validate a particular point - Deut 17:6; Mt 18:16; Jn 8:17; 2Cor 13:1; 1Ti 5:19. (See related comments on Three witnesses).
Brooke adds that "The stress laid by the order upon ‘three’ emphasises this thought of the fulness of the number of the witnesses, and the consequent certainty of that which they affirm. The faith in Jesus as ‘the Christ, the Son of God’ is reasonable according to the ordinary laws of belief." (1 John 5 Commentary - ICC NT Commentary)
Testify (witness)(3140)(martureo from martus/martys = witness = one who has information or knowledge of something and can bring to light or confirm something) in its most basic sense refers to a legal witness. In ancient times on sale documents often several witnesses signed off. Martureo means to be a witness, to testify, to give evidence, to give testimony, to bear record, to affirm that one has seen or heard or experienced something. The words testified related to fact, not opinion, as in a courtroom setting. Martureo is in the present tense signifying that all three witnesses continue to testify to the truth of Jesus Christ. Vine says "the present continuous tense indicates the permanency of the witness."
Hiebert adds that "The present tense points to the fact that the water and the blood continue to bear witness concerning the incarnate Christ whenever the historical facts concerning His baptism and death are read or proclaimed."
Craig Keener on three that testify - Ancient sale documents sometimes included the signatures of several witnesses attesting a sale, and the Old Testament and later Jewish courts always required a minimum of two dependable witnesses (Dt 17:6; 19:15). John cites three witnesses whose reliability could not be in dispute. (The Trinitarian formula found in the KJV of 1Jn 5:7 is orthodox but not part of the text. It appears in only three manuscripts—of the twelfth, fifteenth and sixteenth centuries—out of the thousands available, placed there by scribes who knew it from the Latin Vulgate, which took it from an early marginal note based on a popular early interpretation of the text. The KJV includes it only because that translation was based on a recension dependent on the third edition of Erasmus’s Greek text; Erasmus included the verse to fulfill a wager, protested it in a note and withdrew it in subsequent editions of the text.) (The IVP Bible background commentary: New Testament)