Charles H. Spurgeon on Psalms 59:9

Because of his strength will I wait upon thee. Those seem to come nearest the meaning of the psalmist, who construe the words as one continuous sentence, I will put in trust his strength with thee, meaning that however intemperately Saul might boast of his strength, he would rest satisfied in the assurance that there was a secret divine providence restraining his actions. We must learn to view all men as subordinated in this manner, and to conceive of their strength and their enterprises as depending upon the sovereign will of God. In my opinion, the following version is the best —His strength is with thee, I will wait. The words are parallel with those in the end of the Psalm, where there can be no doubt that the nominative case is employed, My strength is with thee, I will sing. John Calvin.