40 Successus of Abbir Germaniciana said: "Heretics may either do nothing or everything. If they can baptize, they can also give the Holy Spirit; but if they cannot give the Holy Spirit, because they do not possess the Holy Spirit, then can they not either spiritually baptize. Therefore we give our judgment that heretics should be baptized."
41. To this we may answer almost word for word: Murderers may either do nothing or everything. If they can baptize, they can also give the Holy Spirit; but if they cannot give the Holy Spirit, because they do not possess the Holy Spirit, then can they not either spiritually baptize. Therefore we give our judgment that persons baptized by murderers, or murderers themselves who have been baptized without being converted, should, when they have corrected themselves, be baptized. Yet this is not true. For "whosoever hates his brother is a murderer;" and Cyprian knew such men within the Church, who certainly baptized. Therefore it is to no purpose that words of this sort are used concerning heretics.
Source: On Baptism, Against the Donatists (New Advent)