Ante-Nicene Fathers, Vol VIII:
Pseudo-Clementine Literature.: Chapter X

Chapter X.—Why Some Believe, and Others Do Not.

And after Lazarus, Joseph, who also was one of his followers, said:  “You have spoken all things rightly.  Teach me also this, as I am eager to know it, why, when you give the same discourses to all, some believe and others disbelieve?”  And Peter said:  “It is because my discourses are not charms, so that every one that hears them must without hesitation believe them.  The fact that some believe, and others do not, points out to the intelligent the freedom of the will.”  And when he said this, we all blessed him.