4 Certainly, since I found in the letter the copy of which you transmitted to me, that it was written, “That it should not be asked who baptized, since he who is baptized might receive remission of sins according to what he believed,” I thought that this topic was not to be passed by, especially since I observed in the same epistle that mention was also made of Marcion, saying that “even those that came from him did not need to be baptized, because they seemed to have been already baptized in the name of Jesus Christ.” Therefore we ought to consider their faith who believe without, whether in respect of the same faith they can obtain any grace. For if we and heretics have one faith, we may also have one grace. If the Patripassians, Anthropians, Valentinians, Apelletians, Ophites, Marcionites, and other pests, and swords, and poisons of heretics for subverting the truth, confess the same Father, the same Son, the same Holy Ghost, the same Church with us, they may also have one baptism if they have also one faith.
Source: The Epistles of Cyprian (New Advent)