But it is certain that for two reasons the teaching of spiritual things is ineffectual. For either the teacher is commending what he has no experience of, and is trying with empty-sounding words to instruct his hearer, or else the hearer is a bad man and full of faults and cannot receive in his hard heart the holy and saving doctrine of the spiritual man; and of these it is said by the prophet: “For the heart of this people is blinded, and their ears are dull of hearing and their eyes have they closed: lest at any time they should see with their eyes and hear with their ears, and understand with their heart and be converted and I should heal them.”
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 2, vol. 11 (Schaff and Wace, 1894), public domain (Public domain).