The whole of Acts 8:37 of the A.V. is omitted in the R.T., on the authority of the best existing manuscripts. But on the other hand, Irenaeus, in the third book against Heresies, Acts 12:8, distinctly quotes a portion of this verse.
The eunuch, he says, when he asked to be baptized said, πιστεύω τὸν υἱὸν τοῦ θεοῦ εἴναι τὸν ιησοῦν χριστόν: and Cyprian, in his third book of Testimonies, 43., quotes the other part of the verse.
In proof of the thesis that "whoever believes may be immediately baptized," he says, "In the Acts of the Apostles [when the eunuch said], Behold water, what doth hinder me to be baptized? Philip answered, If thou believest with all thine heart, thou mayest."
So that in the second and third centuries, long anterior to the oldest existing manuscripts, this entire verse must have been found in the codices both of the Greek and Latin Churches.