Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 46

Chapter 46.—90.  Litteus 1881 of Gemelli 1882 said:  "‘If the blind lead the blind, both shall fall into the ditch.’ 1883   Since, therefore, it is clear that heretics can give no light 1884 to any one, as being blind themselves, therefore their baptism is invalid." 1885

91.  Neither do we say that it is valid for salvation so long as they are heretics, just as it is of no value to those murderers of whom we spoke, so long as they hate their brethren:  for they also themselves are in darkness, and if any one follows them they fall together into the ditch; and yet it does not follow that they either have not baptism or are unable to confer it.

Footnotes

Some read Licteus; not unlikely the bishop of Cypr. Ep. lxxvi.

Gemelli was a Roman colony in ecclesiastical province of Numidia.

Matt xv. 14.

Illuminare; baptism being often called φωτισμός.

Conc. Carth. sec. 82.