They didn't. I coverd this in post 14. You must not have read it.
First Cyprian:
(1) Cyprian has "
the Father and
the Son and
the Holy Spirit." The Comma has "the Father,
Word, and the Holy Spirit."
(2) Also note in the Latin before each noun there is an "and" (= et).
The Greek text does not.
(4)
The clause "and these three are one" appears in
1 John 5:8.
It is part of the text and does not require the Comma.
(5) Specifically
note what Cyprian does not have: (1) "
For there are three that bear record in heaven," and (2) "
the Spirit, and the Water, and the Blood, and these three agree in one."
Now here is Cyprian's Latin and the Vulgate side by side.
ego et Pater unum sumus. Et iterum Pater et filio et spiritu sancto scriptum est: Et hi tres unum sunt (Cyprian)
et tres sunt, qui testimonium dant in terra: spiritus, et aqua, et sanguis; et hi tres unum sunt (Vulgate)
It is not hard to see they don't really match.
Second, this is one so-called example of the Comma in Tertullian. He writes:
"Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent persons, one from the other, which
three are one, not one [person], as it is said, "I and my Father are One."
Here is the Comma.
For there are three that bear record in heaven, the Father, the Word, and the Holy Spirit: and these three are one. And there are three that bear witness in earth, the Spirit, and the Water, and the Blood, and these three agree in one.
As I pointed out in post 14, the sections
in bold are found in the Greek text. It is
the section in red which is in disputed. This information is necessary to know exactly what is and what is not the Comma.
The Greek text has "For there are three that bear record the Spirit, and the Water, and the Blood, and these three agree in one."
This is no dispute concerning that.
However clearly this is not a quote of the Comma. In fact it is not even a quote at all. Tertullian is expressing his view of the trinity:
"Father in the Son, and of the Son in the Paraclete... ...which
three are one, not one [person]"
This is a clear example of people twisting Tertullian's words in order to force them to fit the Comma in some way.
This is the problem with those who support the Comma. Any phrase, or word that might be even close in the Church fathers they seize no matter how flimsy the resemblance. Often to support their claim they will point to the phrase "these three are one." While this phrase is quote by many Church fathers IT IS NOT PART OF THE DISPUTED SECTION. That section is not part of the disputed text.
A more serious problem is the supporters of the Comma want to change the Greek text because of some quotes from the Latin Church fathers and the Latin text. As I said before, from a text critical perspective, that is a massively poor idea to even think of correcting the Greek text by following the Church fathers or Latin text. If you open the door to those sources for possible which are not found in the Greek text, it will lead to other reading which were never part of the Greek manuscript tradition. Might as well change the Greek text because of the Coptic, Syriac, or Ethiopic versions etc.