Thomas Aquinas, on Ps 18:14

“And from those of others spare thy servant. If they shall have no dominion over me, then shall I be without spot: and I shall be cleansed from the greatest sin.”

“Then he sets forth what pertains to perfection in good. And first, of the mouth; hence he says, "And the words of my mouth shall be such as to please." As long as a man is in sins, his words do not please God: Sir. 15: "Praise is not fitting in the mouth of a sinner": Ps. 49: "But to the sinner God has said: Why do you declare my justices and take my covenant upon your lips?" Likewise, he sets forth the perfection of the heart, which requires the pleasure of God; hence he says, "And the meditation of my heart always in your sight," that is, before the angels; or, "you who see within and examine the conscience." And this I say because you, Lord, are my helper in doing good, and my redeemer from avoiding evils: Is. 44: "Return to me, for I have redeemed you."”

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