Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 10

Chapter 10.—15.  To the declaration of Polycarp of Adrumetum, 1607 that "those who declare the baptism of heretics to be valid, make ours of none effect," we answer, if that is the baptism of heretics which is given by heretics, then that is the baptism of the covetous and murderers which is given by them within the Church.  But if this be not their baptism, neither is the other the baptism of heretics; and so it is Christ’s, by whomsoever it be given.

Footnotes

Adrumetum (Hadrumetum) was an ancient Phœnician settlement, made a Roman colony by Trajan, on the coast of the Sinus Neapolitanus, some ninety miles south-east of Carthage, capital of Byzacium.  Cyprian writes to Bp. Cornelius, Ep. xlviii., vindicating Polycarp:  his name occurs also in the titles of Cypr. Epp. lvii., lxvii. (after Primus), and lxx. (after Cæcilius).