27 But if anyone thinks it open to question whether heretics were always welcomed by our ancestors, let him read the letters of the blessed Cyprian in which he applies the lash to Stephen, bishop of Rome, and his errors which had grown inveterate by usage. Let him also read the pamphlets of Hilary on the re-baptization of heretics which he published against us, and he will there find Hilary himself confessing that Julius, Marcus, Sylvester, and the other bishops of old alike welcomed all heretics to repentance; and, further, to show that he could not justly claim possession of the true custom; the Council of Nicæa also, to which we referred not long ago, welcomed all heretics with the exception of the disciples of Paul of Samosata. And, what is more, it allows a Novatian bishop on conversion to have the rank of presbyter, a decision which condemns both Lucifer and Hilary, since the same person who is ordained is also baptized.
Source: The Dialogue Against the Luciferians (New Advent)