12 Therefore there follows, “Help us, O God, our healing One”. By this word which he says, “our healing One,” he does sufficiently explain what sort of poverty he has willed to be understood, in that which he had said, “for we have become exceeding poor.” For it is that very sickness, to which a healer is necessary. But while he would have us to be aided, he is neither ungrateful to grace, nor does he take away free-will. For he that is aided, does also of himself something. He has added also, “for the glory of Your Name, O Lord, deliver us:” in order that he who glories, not in himself, but in the Lord may glory. “And be merciful,” he says, “to our sins for Your Name's sake:” not for our sake. For what else do our sins deserve, but due and condign punishments? But “be merciful to our sins, for Your Name's sake.” Thus then You deliver us, that is, rescue us from evil things, while You both aid us to do justice, and art merciful to our sins, without which in this life we are not. For “in Your sight shall no man living be justified.” But sin is iniquity. And “if You shall have marked iniquities, who shall stand?”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)