Albert Barnes Commentary Psalms 140:7

"O Jehovah the Lord, the strength of my salvation, Thou hast covered my head in the day of battle." — Psalms 140:7 (ASV)

O God the Lord ... - literally, “Yahweh, Lord, the strength of my salvation.”

The word rendered “God,” in the original, is יהוה Yahweh. The address is to Yahweh as the Lord; that is, as the supreme Ruler—who presides over all things. Him the psalmist acknowledged as “his” Lord and Ruler.

The phrase “the strength of my salvation” means the strength or power on which my safety depends. I have no other hope of deliverance but in You.

You have covered my head in the day of battle - You have been a shield to me. Literally, “In the day of arms,” or of armor, (1 Kings 10:25; Ezekiel 39:9–10).