Sts. Barsanuphius the Great and John the Prophet. "Letters".
LETTER 697
Question: “If, however, the discussion concerns the Scriptures, should I still keep silent, or may I then speak? And if they happen to be unsure of something about which I do know, is it perhaps good for me to speak then or not?” Response by John.
Silence is always better. If, however, they are unsure about something, and you happen to know about this, then in order to solve their doubt, you should say what you know with humility. But if you do not know, then do not say anything at all from your own thought; for this is foolishness.
LETTER 698
Question: “If the conversation concerns various matters that are not harmful to the soul, should I keep silent or speak?” Response.
It is never good to speak before being asked. [171] If you are asked to say something, then say what you know with humility and fear of God. Neither feel arrogant if your words are accepted, nor feel grieved if your words are not accepted. For this is the way of God. [172] Moreover, in order that you may not be considered as being silent, say something from what you know, but be brief and avoid too many words or inopportune glory.
[171] Sayings, Euprepios 7, Poemen 45, and Nau 468.
[172] Cf. Mt 22.16.