12 For it is no small and insignificant matter, which is conceded to heretics, when their baptism is recognised by us; since thence springs the whole origin of faith and the saving access to the hope of life eternal, and the divine condescension for purifying and quickening the servants of God. For if any one could be baptized among heretics, certainly he could also obtain remission of sins. If he attained remission of sins, he was also sanctified. If he was sanctified, he also was made the temple of God. I ask, of what God? If of the Creator; he could not be, because he has not believed in Him. If of Christ; he could not become His temple, since he denies that Christ is God. If of the Holy Spirit; since the three are one, how can the Holy Spirit be at peace with him who is the enemy either of the Son or of the Father?
Source: The Epistles of Cyprian (New Advent)