C. F. Keil and Franz Delitzsch on Psalms 21:13

Psa 21:13 (Hebrew_Bible_21:14) After the song has spread abroad its wings in twice three tetrastichs, it closes by, as it were, soaring aloft and thus losing itself in a distich. It is a cry to God for victory in battle, on behalf of the king. “Be Thou exalted,” i.e., manifest Thyself in Thy supernal (Psa 57:6, 12) and judicial (Psa 7:7.) sovereignty. What these closing words long to see realised is that Jahve should reveal for world-wide conquest this גּבוּרה, to which everything that opposes Him must yield, and it is for this they promise beforehand a joyous gratitude.