26 There is another argument which I shall adduce, and against that not even Hilary, the modern Deucalion, will venture to mutter a syllable. If heretics are not baptized and must be re-baptized because they were not in the Church, Hilary himself also is not a Christian. For he was baptized in that Church which always allowed heretical baptism. Before the Synod of Ariminum was held, before Lucifer went into exile, Hilary when a deacon of the Roman Church welcomed those who came over from the heretics on account of the baptism which they had previously received.
It can hardly be that Arians are the only heretics, and that we are to accept all but those whom they have baptized. You were a deacon, Hilary (the Church may say), and received those whom the Manichæans had baptized. You were a deacon, and acknowledged Ebion's baptism. All at once after Arius arose you began to be quite out of conceit with yourself. You and your household separated from us, and opened a new laver of your own. If some angel or apostle has re-baptized you, I will not disparage your procedure.
But since you who raise your sword against me are the son of my womb, and nourished on the milk of my breasts, return to me what I gave you, and be, if you can, a Christian in some other way. Suppose I am a harlot, still I am your mother. You say, I do not keep the marriage bed undefiled: still what I am now I was when you were conceived. If I commit adultery with Arius, I did the same before with Praxias, with Ebion, with Cerinthus, and Novatus. You think much of them and welcome them, adulterers as they are, to your mother's home. I don't know why one adulterer more than others should offend you.
Source: The Dialogue Against the Luciferians (New Advent)