Albert Barnes Commentary Psalms 63:11

"But the king shall rejoice in God: Every one that sweareth by him shall glory; For the mouth of them that speak lies shall be stopped." — Psalms 63:11 (ASV)

But the king shall rejoice in God - This passage, as was noted in the Introduction to the psalm, shows that this psalm could not have been composed in the time of Saul, since the title "king" was not then given to David. The use of the term here in the third person does not prove that the psalm could not have been written by David himself, for he might have spoken of himself simply as “the king,” and all the more forcefully and appropriately as he was driven unjustly from his throne, and was now an exile, yet was still a king—the king.

The title was his; the throne belonged to him, and not to Absalom who had driven him from it. It was not improper to allude to this fact in the way it is referred to here, and to say that “the king”—the true, the real king—himself—should and would rejoice in God.

He would find God to be his helper; and by God he would still be restored to his throne.

Every one that sweareth by him shall glory - Everyone that swears to him, or maintains his oath of allegiance to him, will be honored.

But the mouth of them that speak lies - All who have sworn falsely, all who have professed allegiance and have proved unfaithful, and all those who, contrary to their oaths and their obligations, have been found in the rebellion, will not be permitted to exult or rejoice, but they will be confounded and silenced.

This expresses, therefore, the fullest confidence in God: the absolute belief of David that he would be placed on his throne again, and again permitted to see the power and glory of God as he had seen it in the sanctuary (Psalms 63:2); the belief that he would be restored to prosperity, and that his enemies would be humbled and destroyed. So it will be with all who put their trust in God. There is certain joy and triumph for them, if not in this world, at least in the world to come.