John Calvin Commentary Psalms 144:1

"Blessed be Jehovah my rock, Who teacheth my hands to war, [And] my fingers to fight:" — Psalms 144:1 (ASV)

Blessed be Jehovah, my strength. It is very evident that David, because he celebrates the favor of God in such high terms, had not only obtained the kingdom, but gained significant victories.

When he calls God his strength, he acknowledges that any courage he possessed was given to him from above. This was not only because he had been transformed from a country shepherd into a mighty warrior, but also because the constancy and perseverance he had shown was remarkably a gift from God.

This term is more fitting than if we were to translate it "rock"; for, by way of explanation, he immediately adds that he had been formed under God’s teaching for war. The words certainly imply an acknowledgment that, although he had a warlike spirit, he was not born for warlike enterprises but needed to undergo a change.

What kind of a beginning, for example, did he show in the case of Goliath? That attempt would have been preposterous unless he was upheld by secret divine support, making him independent of mere human help (1 Samuel 17:40).