3 But among us it is no new or sudden thing for us to judge that those are to be baptized who come to the Church from among the heretics, since it is now many years and a long time ago, that, under Agrippinus— a man of worthy memory— very many bishops assembling together have decided this; and thenceforward until the present day, so many thousands of heretics in our provinces have been converted to the Church, and have neither despised nor delayed, nay, they have both reasonably and gladly embraced, the opportunity to attain the grace of the life-giving layer and of saving baptism. For it is not difficult for a teacher to insinuate true and lawful things into his mind, who, having condemned heretical pravity, and discovered the truth of the Church, comes for this purpose, that he may learn, and learns for the purpose that he may live. We ought not to increase the stolidity of heretics by the patronage of our consent, when they gladly and readily obey the truth.
Source: The Epistles of Cyprian (New Advent)