The king shall joy in your strength, O LORD; and in your salvation how greatly shall he rejoice!
Read Chapter 21
Augustine of Hippo
AD 430
2. "O Lord, the King shall rejoice in Thy strength" (ver. 1). O Lord, in Thy strength, whereby the Word was made flesh, the Man Christ Jesus shall rejoice. "And shall exult exceedingly in Thy salvation." And in that, whereby Thou quickenest all things, shall exult exceedingly.
King. Chaldean adds, "the Messias shall reign; and how shall he rejoice when thou shalt have delivered him! "The people had promised to return thanks in the former psalm. (Haydock)
Christ our king as man, having by his divine power overcome his enemies, rejoiceth. (Worthington)
David, after his victory over the Ammonites; (Du Pin; Calmet) though many passages relate only to the Messias, as the Chaldean and even some of the modern Jews confess, (Kimchi; Muis) with the holy Fathers, who explain all of Him. (Calmet)
Those who overcome the devil, are here concerned. (Worthington)