3 For how did He turn away the captivity of Jacob? See, how that that setting free is spiritual, see how that it is done inwardly. “You have forgiven,” he says, “the iniquity of Your people: You have covered all their sins”. Behold how He has turned away their captivity, in that He has remitted iniquity: iniquity held them captive; your iniquity forgiven, you are freed. Confess therefore that you are in captivity, that you may be worthy to be freed: for he that knows not of his enemy, how can he invoke the liberator? “You have covered all their sins.” What is, “You have covered”? So as not to see them. How did You not see them? So as not to take vengeance on them. You were unwilling to see our sins: and therefore You saw them not, because You would not see them: “You have covered all their sins.” “You have appeased all Your anger: You have turned Yourself from Your wrathful indignation”.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)