Albert Barnes Commentary Psalms 44:4

"Thou art my King, O God: Command deliverance for Jacob." — Psalms 44:4 (ASV)

You are my King, O God - literally, “You are He, my King, O God”; that is, You are the same: the same King, and the same God, who intervened in the time of the fathers. You are also the one whom I recognize as King, as the Sovereign Ruler of Your people. The psalmist here uses the singular number, “my King,” to express his own feelings, though he doubtless also means to speak in the name of the people. It seems likely from this that the author of the psalm was the reigning monarch during the time of the troubles referred to. If not, it was evidently one who assumed his role and intended to represent his feelings.

The language shows the strong confidence of the author of the psalm in God, and perhaps also is designed to express his personal responsibility at the time, and his awareness that his only refuge in conducting the troubled affairs of the nation was God.

Command deliverances for Jacob - It is as if everything was under His command, and He only had to give direction, and salvation would come. The word “Jacob” here is used to denote the descendants of Jacob, or the people of God. See the notes at Psalms 24:6.