The position in the question, that Father, Son, and Holy Spirit is not original to Matthew 28:19 is held today by very few scholars. Those that do point to a quotation from the early church historian Eusebius. In Demonstratio 3.6, he replaces "name of the Father, Son, and Holy Spirit" with "my name."
This is then taken as a direct quote from the copy of Matthew he was using and the conclusion is then reached that the long version of Matthew 28:19 was added later. Also, it is concluded that the short reading was purposefully suppressed.
The originality of the short version of the verse fails in regards to both physical/manuscript evidence and logic.
Manuscript Evidence I: Matthew
Even though critics of trinitarians claim there is a mountain of historical evidence, there actually isn't. Another answer on this site lays out the manuscripts of Matthew. No manuscript of Matthew is known that has the short form of the verse. Even though the critical texts used by scholars lay out all kinds of textual variants throughout the NT, my copy of NA-27 does not list any variants on Matthew 28:19. Even though it lists out variants on 18 and 20, there are none for 19. When looking beyond Greek, all ancient translations have the long reading of Matthew (Latin, Syriac, etc).
One might point out the Hebrew translation of Matthew known as Shem Tob. While it does not have the long reading, it does not count for several reasons.
- It dates from the late 1300s (the medieval period, not antiquity). Far too late to be of any significant textual help.
- It doesn't even have the short reading of "baptizing in my name." Instead, Matt 28:19-20 reads "Go and teach them to carry out all the things which I have commanded you forever." It mentions nothing of baptizing at all.
Bart Ehrman, a noted textual critic who is neither a Christian nor a trinitarian (in fact, he describes himself as an agnostic) agrees that the long form of the verse is original. The same blog reproducing Ehrman on this passage has a statement from another New Testament scholar who is also an authority on Eusebius. He notes:
- Eusebius' short form (Demonstratio 3.6, 7(bis); 9.11; Hist. Eccl. III.5.2; Psalms 65.6; 67.34; 76.20 (59.9 not the same reading); Isaiah 18.2; 34.16 (v.l.); Theophania 4.16; 5.17; 5.46; 5.49; Oratio 16.8) is the only textual evidence for the short reading
- Eusebius tends to abbreviate elsewhere
- Eusebius quotes the long form in Contra Marcellum I.1.9; I.1.36; Theologia III. 5.22; EpCaesarea 3 (Socrates, Eccl.Hist 1.8); Psalms 117.1-4; and Theophania 4.8
It is worth noting that Eusebius in Demonstratio Evangelica, one of the places where he is supposed to be quoting the short version of Matthew 28:19, also "quotes" Philippians 2:9. However, the statement is certainly not a quotation:
Eusebius writes is as:
God bestowed on him the name above every name, that in the name of Jesus every knee shall bow of things in heaven and on earth and under the earth.
However, the full text is:
Wherefore God also hath highly exalted him, and given him a name which is above every name: That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth;
Eusebius is certainly refering to Phil 2:9f, but his writing of it is not a quotation.
Manuscript Evidence II: Quotation from the Church Fathers
Text critics don't just look at manuscripts of the text. They also examine quotations of passages in early writers. All quotations of Matthew 28:19 that include the "name" formula have the long version and not the short.
- Didache 7:1 Concerning baptism, you should baptize this way: After first explaining all things, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in flowing water
- Tertullain On Baptism paragraph 13 Go, he says, teach the nations, baptizing them in the Name of the Father and the Son and the Holy Ghost.
- Tertullian Against Praxeas, chapter 2 says, "After His resurrection ..He commands them to baptize into the Father and the Son and the Holy Ghost".
- Gregory Thaumaturgus (205-265 AD) in A Sectional Confession of Faith, XIII
- Hippolytus (170-236 AD says in Fragments: Part II.-Dogmatical and Historical.--Against the Heresy of One Noetus,
- Cyprian (200-258AD) in The Seventh Council of Carthage Under Cyprian
- and others
In total, searching only those Fathers prior to Nicea, I found 24 quotations of Matthew 28:19 using the full formula. There were no quotations amongst these writers with the short version. There were also quotations of the verse where they stopped prior to the list of names (i.e. "he commanded us to teach all nations"). I did not count those. In several of these, the full quote provides the basis for the argument supplied in the rest of the paragraph.
Triune Formulas Elsewhere in the New Testament
Even if Matthew 28:19 as we now know it is an addition, that does not eliminate the other trinitarian formulas present in the New Testament.
- At the baptism of Jesus, all three persons are present (Matthew 3:16-17; Mark 1:10-11; Luke 3:21-22; John 1:32).
- 2 Corinthians 13:14 The grace of the Lord Jesus Christ, the love of God, and the communion of the Holy Spirit be with all of you
- 1 Peter 1:2-3a ...who have been chosen and destined by God the Father and sanctified by the Spirit to be obedient to Jesus Christ and to be sprinkled with his blood: May grace and peace be yours in abundance. Blessed be the God and Father of our Lord Jesus Christ!
A third way in which the longer form can be seen to be original is to simply apply logic to the argument for the shorter as a conspiracy. The argument is that some faction of the Church (obviously representing the majority as this view won):
- Wanted the trinity formula in Matthew.
- Willfully altered manucsripts of Matthew 28:19.
- Sought out and destroyed all manuscripts of Matthew 28:19 containing the short reading.
- Then went through the writings of the Ante-Nicean Fathers and altered their quotations of Matthew, destroying all other copies.
However, these conspirators, who had so little respect for Scripture that they altered it and were so careful as to destroy every copy of Matthew with the short reading, left intact the so-called original verse in Luke 24:47 (which is not a baptismal formula and is not a parallel to Matthew 28:19)* and all references to Jesus' name baptism in Acts and the Epistles! If this willful alteration is being done in Matthew, why stop there? Why not change Luke 24:47; Acts 2:38; 8:12, 16; 10:48; and 19:5? These five verses in Acts all refer to Jesus' name baptism or being baptized in Jesus' name (once, in the name of our Lord). None of them have textual variants of a trinitarian formula. Logically, if the conspirators made the change once, they would make the change in other places. At the time which this conspiracy is supposed to have taken place (Nicea, AD 325), the de-facto canon had been used and recognized since Iraneus. Matthew, Luke, and Acts were already recognized as Scripture.
*Matthew 28 takes place in Galillee while Luke's is in Jerusalem. Luke contains only statements of repentance and remission of sins while Matthew also speaks of teaching and baptism.
Another failing of this conspiracy is that they missed Eusebius, one of their contemporaries. Eusebius was a trinitarian and a powerful figure in the church. Yet, while they changed all quotations of Matthew 28:19 from the short to long in all the Ante-Nicean Church Fathers, they missed a few places in Eusebius but got his others. How did they manage to get all of the others yet miss some of one of their own?
If this were a conspiracy, it was a rather inept conspiracy as it left intact so many other verses in Scripture while managing to replace all versions of Matthew 28:19 with the new one.