LET US DO what the Prophet says: "I said, 'I will guard my ways, that I may not sin with my tongue. I have set a guard to my mouth.' I was mute and was humbled, and kept silence even from good things". Here the Prophet shows that if the spirit of silence ought to lead us at times to refrain even from good speech, so much the more ought the punishment for sin make us avoid evil words.
Rule of St Benedict, chapter 6