5 But since that messenger sent by you was in haste to return to you, and the winter season was pressing, we replied what we could to your letter. And indeed, as respects what Stephen has said, as though the apostles forbade those who come from heresy to be baptized, and delivered this also to be observed by their successors, you have replied most abundantly, that no one is so foolish as to believe that the apostles delivered this, when it is even well known that these heresies themselves, execrable and detestable as they are, arose subsequently; when even Marcion the disciple of Cerdo is found to have introduced his sacrilegious tradition against God long after the apostles, and after long lapse of time from them.
Apelles, also consenting to his blasphemy, added many other new and more important matters hostile to faith and truth. But also the time of Valentinus and Basilides is manifest, that they too, after the apostles, and after a long period, rebelled against the Church of God with their wicked lies. It is plain that the other heretics, also, afterwards introduced their evil sects and perverse inventions, even as every one was led by error; all of whom, it is evident, were self-condemned, and have declared against themselves an inevitable sentence before the day of judgment; and he who confirms the baptism of these, what else does he do but adjudge himself with them, and condemn himself, making himself a partaker with such?
Source: The Epistles of Cyprian (New Advent)