Blessing. David seems to have given the eulogium of Obededom, whose example taught him that the ark was only terrible to the wicked; and that it was a source of blessings to the just, 2 Kings vi. 11.
Mercy. Hebrew, "justice. "But these terms are used synonymously, and denote that God gives a just reward; "when he crowns our merits, he crowns his own gifts. "(St. Augustine; Theodoret) (Calmet)
Mercy goes before; good works must follow, to obtain eternal glory. (Worthington)