17 And in this respect I am justly indignant at this so open and manifest folly of Stephen, that he who so boasts of the place of his episcopate, and contends that he holds the succession from Peter, on whom the foundations of the Church were laid, should introduce many other rocks and establish new buildings of many churches; maintaining that there is baptism in them by his authority. For they who are baptized, doubtless, fill up the number of the Church. But he who approves their baptism maintains, of those baptized, that the Church is also with them.
Nor does he understand that the truth of the Christian Rock is overshadowed, and in some measure abolished, by him when he thus betrays and deserts unity. The apostle acknowledges that the Jews, although blinded by ignorance, and bound by the grossest wickedness, have yet a zeal for God. Stephen, who announces that he holds by succession the throne of Peter, is stirred with no zeal against heretics, when he concedes to them, not a moderate, but the very greatest power of grace: so far as to say and assert that, by the sacrament of baptism, the filth of the old man is washed away by them, that they pardon the former mortal sins, that they make sons of God by heavenly regeneration, and renew to eternal life by the sanctification of the divine layer.
He who concedes and gives up to heretics in this way the great and heavenly gifts of the Church, what else does he do but communicate with them for whom he maintains and claims so much grace? And now he hesitates in vain to consent to them, and to be a partaker with them in other matters also, to meet together with them, and equally with them to mingle their prayers, and appoint a common altar and sacrifice.
Source: The Epistles of Cyprian (New Advent)