Psalms 144:9

The method is the same in this latter part of the psalm as in the former; David first gives glory to God and then begs mercy from him. I. He praises God for the experiences he had had of his goodness to him and the encouragements he had to expect further mercy from him, Psa 144:9, Psa 144:10. In the midst of his complaints concerning the power and treachery of his enemies, here is a holy exultation in his God: I will sing a new song to thee, O God! a song of praise for new mercies, for those compassions that are new every morning. Fresh favours call for fresh returns of thanks; nay, we must praise God for the mercies we hope for by his promise as well as those we have received by his providence, Ch2 20:20, Ch2 20:21. He will join music with his songs of praise, to express and excite his holy joy in God; he will praise God upon a psaltery of ten strings, in the best manner, thinking all little enough to set forth the praises of God. He tells us what this new song shall be (Psa 144:10): It is he that giveth salvation unto kings. This intimates, 1. That great kings cannot save themselves without him.

— Matthew Henry's Concise Commentary (public domain)