Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 29

Chapter 29.—56.  Quintus of Aggya 1837 said:  "He who has a thing can give it; but what can the heretics give, who are well known to have nothing?" 1838

57.  To him our answer is:  If, then, any man can give a thing who has it, it is clear that heretics can give baptism:  for when they separate from the Church, they have still the sacrament of washing which they had received while in the Church; for when they return they do not again receive it, because they had not lost it when they withdrew from the Church.

Footnotes

Aggya, probably the same as Aggiva and the Aga in ecclesiastical province of Proconsular Africa.  The name Quintas as bishop occurs in Cypr. Epp lvii., lxvii., lxx., lxxi., but this one is of Mauritania, as appears from Epp lxxii. 1, lxxiii. 1.

Conc. Carth. sec. 65.