16 “But I with My prayer with You, O Lord”. But I was with You. But how? With You by praying. For when you are evil spoken of, and know not what you may do; when at you are hurled reproaches, and you find not any way of rebuking him by whom they are hurled; nothing remains for you but to pray. But remember even for that very man to pray. “But I with my prayer with You, O Lord. It is the time of Your good pleasure, O God.” For behold the grain is being buried, there shall spring up fruit.
“It is the time of Your good pleasure, O God.” Of this time even the Prophets have spoken, whereof the Apostle makes mention: “Behold now the time acceptable, behold now the day of salvation.” “It is the time of Your good pleasure, O God. In the multitude of Your mercy.” This is the time of good pleasure, “in the multitude of Your mercy.” For if there were not a multitude of Your mercy, what should we do for the multitude of our iniquity? “In the multitude of Your mercy; Hearken to me in the truth of Your Salvation.” Because He has said, “of Your mercy,” he has added truth also: for “mercy and truth” are all the ways of the Lord. Why mercy? In forgiving sins. Why truth? In fulfilling the promises.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)