Gregory the Great, on Isa 6:5

“And I said: Woe is me, because I have held my peace; because I am a man of unclean lips, and I dwell in the midst of a people that hath unclean lips, and I have seen with my eyes the King the Lord of hosts.”

“Purity of heart and simplicity, Peter, is of great force with almighty God, who is in purity most singular, and of nature most simple. For those servants of his, which do retire themselves from worldly affairs, avoid idle words, labour not to lose their devotion, nor to defile their soul with talking, do especially obtain to be heard of him, to whom, after a certain manner, and as they may, they be like in purity and simplicity of heart. But we that live in the world, and speak oftentimes idle words, and that which is worse, sometime those that be hurtful: our words and prayers are so much the farther off from God, as they be near unto the world: for we are drawn too much down towards the earth, by continual talking of secular business: which thing the prophet Esaye did very well reprehend in himself, after he had beheld the King and Lord of armies, and was penitent, crying out: Woe be to me for being silent, because I am a man that have defiled lips: and he sheweth straight after the reason why his lips were defiled, when he saith: I dwell in the midst of a people that hath defiled lips. For sorry he was that his lips were defiled, yet concealeth not from whence he had them, when he saith, that he dwelt in the midst of a people that had defiled lips. For very hard it is that the tongues of secular men should not defile their souls, with whom they talk; for when we do sometime condescend to speak with them of certain things, by little and little we get such a custom, that we hear that spoken with pleasure which is not meet to be heard at all, so that afterward we are loath to give that over, to which at the first, to gratify others, we were brought against our wills. And by this means we fall from idle words to hurtful speeches, and from talk of small moment to words of great importance: and so it cometh to pass that our tongue is so much the less respected of God when we pray, by how much we are more defiled with foolish speech, because, as it is written: He that turneth away his ear that he hear not the law, his prayer shall be execrable. What marvel, then, is it, if, when we pray, God doth slowly hear us, when as we hear God's commandments, either slowly or not at all?”

Imported from an open dataset — not yet checked against the printed edition.