5 “I acknowledged my sin, and my unrighteousness have I not hid:” that is, my unrighteousness have I not concealed. “I said, I will confess against myself my unrighteousness to the Lord:” I said, I will confess, not against God (as in my ungodly crying, when I kept silence), but against myself, my unrighteousness to the Lord. “And Thou forgavest the iniquity of my heart”; hearing the word of confession in the heart, before it was uttered with the voice.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)