My strength is with thee, I will sing psalms He expresses still more explicitly the truth, that he owed his safety entirely to God. Formerly he had said that the strength of his enemy was with God, and now he asserts the same thing of his own. The expression, however, which admits of two meanings, he elegantly applies to himself in a different sense. God has the strength of the wicked in his hands, to curb and to restrain it, and to show that any power of which they boast is vain and fallacious. His own people, on the other hand, he supports and secures, against the possibility of falling, by supplies of strength from himself. In the preceding part of the psalm, David had congratulated himself upon his safety, by reflecting that Saul was so completely under the secret restraint of God's providence as to be unable to move a finger without his permission. Now, weak as he was in himself, he maintains that he had strength sufficient in the Lord; and accordingly adds, that he had good reason to engage in praise, as James the inspired apostle exhorts those who are merry to sing psalms, (James 5:13.) As to the reading which some have adopted, I will ascribe my strength with praises unto thee, the reader cannot fail to see that it is forced. It is clear that the two clauses must be taken separately, as I have already observed.

Unto thee, O my strength, will I sing - The source of strength to me; the real strength by which I have obtained deliverance is in thee. See the notes at Psalm 18:1.
For God is my defense - See the notes at Psalm 59:9.
And the God of my mercy - The God who has showed mercy to me; he from whom all these favors have sprung. Whatever means might be used to secure his own safety (compare 1-Samuel 19:12 ff) still he felt that his deliverance was to be traced wholly to God. He had interposed and had saved him; and it was proper, therefore, that praise should be ascribed to him. The experience of David in the case referred to in this psalm should be an inducement to all who are in danger to put their trust in God; his anticipated feelings of gratitude, and his purpose to praise God when he should be delivered, should awaken in us the resolution to ascribe to God all the praise when we are delivered from impending troubles, and when our lives are lengthened out where we have been in imminent danger. Whatever may have been the means of our rescue, it is to be traced to the interposition of God.

Unto thee, O my strength - A similar sentiment to that expressed, Psalm 59:9. But the words are very emphatic: God is my strength; God is my elevation. My God is my mercy. I have nothing good but what I have from God. And all springs from his dwelling in me. God, therefore, shall have all the glory, both now and for ever.
As many persons may still think that the inscription to this Psalm is correct, the following analysis may be applied in that way; or considered as containing a general resolution of the Psalm, without referring it to any particular occasion.

Unto thee, O my (o) strength, will I sing: for God [is] my defence, [and] the God of my mercy.
(o) Confessing himself to be void of all virtue and strength, he attributes the whole to God.

Unto thee, O my strength, will I sing,.... That is, to God, whom he made his strength, and put his trust in for strength, and from whom he received it; and he therefore determined to sing praise to him for it, and give him the glory of it;
for God is my defence: as before in Psalm 59:9;
and the God of my mercy; See Gill on Psalm 59:10.