Ante-Nicene Fathers Volume 5
Cyprian: Epistles LXIX-LXXI
These Epistles begin a series on the nature of baptism, and what to do when heretics attempt it. In Epistle LXIX, Cyprian writes to the pastors he had been in council with and notes that this decision should be made by the group, not by any one church or pastor. Yet, they all agree that there is only one baptism and it can only be performed by the church. Specifically, "It is required, then, that the water should first be cleansed and sanctified by the priest [elder], that it may wash away by its baptism the sins of the man who is baptized..." This practice should be followed by anointing with oil from the Lord's Table. However, each of these, if performed by a heretic, is illegitimate and needs to be repeated when the individual comes into the church proper.
While Cyprian's point about baptism by heretics and his desire to maintain the unity of the church are both well taken, his view of what happens in baptism (namely the washing away of sins and the bestowing of the Holy Spirit) is simply false. It's true that regeneration comes by means of the baptism of the Holy Spirit, and it's further true that such baptism means being drawn into the body of believers, the true church. But this must not be confused with the outward symbol we exercise when we declare this truth within the body with physical water. The former is an act of God directly upon the soul, the latter an act of obedience by the individual Christian and the church.
Cyprian repeats this argument in Epistle LXX, emphasizing that heretic baptism is no true baptism. And for what it's worth, I'm on board with at least that part of his claim. One who comes to the faith after having been baptized in a Mormon or Catholic church does need to be actually baptized by a Christian congregation. Cyprian is also correct that in part we do this so we are not legitimating the heretical church, he's just wrong about the proper mode of baptism. If one is baptized in a faithful church, goes to the heretics, and then comes back, Cyprian thinks they need not be rebaptized. I am undivided on that, but willing to go along for the sake of peace. Fortunately, Cyprian promises flexibility: "Neither must we prescribe this from custom, but overcome opposite custom by reason... we should not obstinately love our own opinions, but should rather adopt as our own those which at any time are usefully and wholesomely suggested by our brethren and colleagues, if they be true and lawful." So there's hope!
Epistle LXXI is from Cyprian to Stephen, pastor of the Roman church, informing him about the decisions of the council in North Africa concerning baptism by heretics. Most of the teachings we've already seen--both true and false, show up again in summary form.