I was researching the Trinity to defend the Catholic position to a pentecostal friend of mine. I found a couple of tracts on Catholic Answers, God in Three Persons was one of them.
Fulgentius of Ruspe refers to 1 John 5:7:
“And there are three who give testimony in heaven, the Father, the Word, and the Holy Ghost. And these three are one.” (Douay-Rheims version only)
This same passage is not found in other versions. I had an RSV-CE version I was looking at, and it did not appear. I check the New American, not there. New Jerusalem, again, that passage does not exist. What happened to this mention of the Trinity in these other translations?
Douay-Rheims: 6 This is he that came by water and blood, Jesus Christ: not by water only, but by water and blood. And it is the Spirit which testifieth, that Christ is the truth. 7 And there are three who give testimony in heaven, the Father, the Word, and the Holy Ghost. And these three are one. 8 And there are three that give testimony on earth: the spirit, and the water, and the blood: and these three are one.
RSV-CE: 6 This is he who came by water and blood, Jesus Christ, not with the water only but with the water and the blood. 7 And the Spirit is the witness, because the Spirit is the truth. 8 There are three witnesses, the Spirit, the water, and the blood; and these three agree.
NAB: 6 This is the one who came through water and blood, Jesus Christ, not by water alone, but by water and blood. The Spirit is the one that testifies, and the Spirit is truth. 7 So there are three that testify, 8 the Spirit, the water, and the blood, and the three are of one accord.
NJ: 6 He it is who came by water and blood, Jesus Christ, not with water alone but with water and blood, and it is the Spirit that bears witness, for the Spirit is Truth. 7 So there are three witnesses, 8 the Spirit, water and blood; and the three of them coincide.