Albert Barnes Commentary Psalms 108:13

"Through God we shall do valiantly: For he it is that will tread down our adversaries." — Psalms 108:13 (ASV)

Through God we shall do ... — This is also taken from Psalms 60:12, without change.

Thus, the psalm, although composed of parts from two separate psalms, is complete and continuous in itself. There is no break or discrepancy in the flow of thought; its unity is as perfect as if it had been an original composition.

It should also be noted that although the parts used here have a different connection in the original psalms and are complete in themselves there, yet when used here, they seem perfectly suited to the new application of the language. And although the original reasons for using this language do not appear here, a sufficient reason for it is evident in the psalm as rearranged.

An Israelite might also find new interest in this use of language: words familiar to him from other contexts could now be combined and applied to a new event in the nation's history.