John Calvin Commentary Psalms 44:4

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

Thou, even thou, art my King, O God! In this verse the faithful express still more plainly what I have already alluded to a little earlier: that the goodness of God was not only apparent in the deliverance of His people but also flowed to them in continuous succession from age to age. Therefore, it is said, Thou, even thou, art my King.

In my judgment, the demonstrative pronoun הוא, hu, means as much as if the prophet had compiled a long series of God's benefits after the first deliverance. This was so that it might appear that God, who had once been the deliverer of His people, did not act differently toward their descendants.

Alternatively, it might be considered emphatic, used to assert the statement more strongly: that the faithful praise God alone as the guardian of their welfare, excluding all others and renouncing aid from any other source.

Therefore, they also offer the prayer that God would ordain and send out new deliverances to His people. For, since He has in His power innumerable means of preservation and deliverance, He is said to appoint and send out deliverances as His messengers wherever it seems good to Him.