Blessed is he, literally, "O the blessings of him," those which he possesses, whose transgression is forgiven, not condoned, but taken away, whose sin is covered, so that the just and holy God no longer sees it, as it were. In what sense this is possible is shown in the next verse.
Related Commentaries of Psalms 32:1
Psalms 32:1
1 Blessed is he whose transgression is forgiven, whose sin is covered.