Albert Barnes Commentary Psalms 18:39

"For thou hast girded me with strength unto the battle: Thou hast subdued under me those that rose up against me." — Psalms 18:39 (ASV)

For thou hast girded me with strength unto the battle - See the note at (Psalms 18:32). Compare (Job 12:18); (Proverbs 31:17).

Thou hast subdued under me - Margin, as in Hebrew, caused to bow. That is, God had caused them to submit to him; he had enabled him to overcome them, still acknowledging that all this was from God, and that the praise was due to Him, and not to the power of his own arm.