On profitable Conversation:

Silence of the lips is better and more wonderful than any edifying conversation. Our fathers embraced it with reverence and were glorified through it. But since, in our weakness, we cannot yet follow the path of the perfect, let us talk of what edifies, and speak of such things with reference to the words of the fathers, without undertaking to interpret the Scriptures; for this latter is fraught with dangers for the ignorant. The Scriptures are written in the language of the spirit, and men of the flesh cannot understand spiritual things. It is best to use the words of the fathers in our conversations; then we shall find the profit they contain.

Sts. Barsanuphius and John, Directions, Philokalia, B#23, p.93