John Calvin Commentary Psalms 89:42

"Thou hast exalted the right hand of his adversaries; Thou hast made all his enemies to rejoice." — Psalms 89:42 (ASV)

Thou hast exalted the right hand of his oppressors. Here he states that God took part with the enemies of the king, for he was well aware that these enemies could not have prevailed except by the will of God, who inspires some with courage and renders others faint-hearted.

In short, in proportion to the number of calamities that had befallen the chosen people, so was the number of evidences that they had been forsaken by God. For, as long as he continued his favor, the whole world, by all their machinations, was unable to impair the stability of that kingdom.

Had it been said that the enemies of the king obtained the victory, the statement would have been quite true, but it would not have been a mode of expression so obviously fitted to exalt the Divine power; for it might have been thought that people setting themselves in opposition to God had, by their own power, forced their way and effected their purpose, even against those who enjoyed his protection.

Accordingly, the prophet reflects with himself that unless the Divine anger had been incensed, that kingdom that God had erected could not have been reduced to a condition so extremely wretched.