Albert Barnes Commentary Psalms 3:7

"Arise, O Jehovah; save me, O my God: For thou hast smitten all mine enemies upon the cheek bone; Thou hast broken the teeth of the wicked." — Psalms 3:7 (ASV)

Arise, O Lord - This is a common way of calling upon God in the Scriptures, as if He had been sitting still, or had been inactive. It is, of course, language taken from human conceptions, for in the intervals of active effort, in labor or in battle, we sit or lie down, and when we engage in toil we arise from our sitting or resting posture. So the mind accustoms itself to think of God. The idea is simply that David now calls upon God to interpose on his behalf and to deliver him.

Save me, O my God - He was still surrounded by numerous enemies, and he, therefore, calls earnestly upon God to help him. In accordance with a common usage in the Scriptures, and with what is right for all the people of God, he calls Him “his” God: O my God. That is, He was the God whom he recognized as his God, in distinction from all idols, and who had manifested Himself as his God by the many mercies which He had conferred on him.

For thou hast smitten all mine enemies - That is, in previous urgent situations, or on former occasions. In his conflicts with Saul, with the Philistines, and with the surrounding nations, God had done this; and as the result of all, He had established him on the throne and placed him over the realm. In the remembrance of all this, he appeals with full confidence that what God had done for him before, He would do now, and that, even though he was surrounded with numerous foes, He would again interpose.

So we may derive comfort and assurance in present trouble or danger from the recollection of what God has done for us in former times. He who has saved us in former perils can still save us; we may believe that He who did not forsake us in those perils will not leave us now.

Upon the cheek-bone - This language seems to be taken from a comparison of his enemies with wild beasts. The idea is that God had disarmed them as one would a lion or tiger by breaking its teeth. The cheek-bone denotes the bone in which the teeth are placed; and to strike that is to disarm the animal. The idea here is not that of “insult,” therefore; but the meaning is simply that He had deprived them of the power of doing him wrong.

Thou hast broken the teeth of the ungodly - The same idea is expressed here under another form, “as if” the teeth of wild animals were broken out, rendering them harmless. As God had thus disarmed his enemies in times past, the psalmist hoped that He would do the same thing now, and he confidently called on Him to do it.