Surely our heart shall rejoice in him. As the particle ky, ki, which is twice employed in this verse, has various meanings in Hebrew, it may be understood in a twofold sense here. If we expound it affirmatively in both clauses, the sense will be, that believers glory both in their joy and in their hope. Nor do I think it improper that these two should be referred to distinctly in the same context thus: Surely God shall always be our joy; surely his holy name shall be like an impregnable fortress for our refuge. Whence is it that believers continue perseveringly to call upon God, but because, satisfied with his favor, they have always, amidst their sorrows and griefs, this comfort, which is sufficient to maintain their cheerfulness? Justly, therefore, do believers affirm, in the first place, that their heart rejoices in the Lord; because, freed from wandering after the fascinations of the world, they neither waver nor hesitate at every change of fortune, but place the whole felicity of their life in enjoying the free and paternal favor of God. They afterwards add, in the second place, that they trust in his holy name. If any one, however, choose to understand the particle ky, ki, as meaning because, assigning a cause or reason, the sense will be no less properly and elegantly expressed in this way: Because our hope is fixed on God, he will be equally ready on his part to minister to us continual matter of joy. And experience undoubtedly proves, that when men are overwhelmed with sorrow, and pine away with care, grief, and anxiety, it is that they may receive the recompense of their folly; seeing that there is nothing to which they are led with more difficulty, than to set their hopes on God alone, and not to exult in their own deceitful imaginations, with which they please themselves.

For our heart shall rejoice in him - See the notes at Psalm 13:5.
Because we have trusted in his holy name - In "him," the "name" often being put for the person himself. See the notes at Psalm 20:1. The idea is:
(a) that the fact of our having put our trust in God is in itself an occasion of joy or rejoicing;
(b) that the result will be joy, for we shall never be disappointed.
It will always, and in all circumstances, be a source of joy to anyone that he HAS put his trust in the name of God.

For our heart shall rejoice in him - Here is the fruit of our confidence: our souls are always happy, because we have taken God for our portion.

For our heart shall rejoice in him,.... Not in sin, nor in themselves and in their boastings, all such rejoicing is evil; but in the Lord, "in his Word"; as the Targum is, in the essential Word of God, Christ Jesus; in his person, righteousness, and salvation; and this joy is heart joy, inward joy, real joy, joy in the Holy Ghost; and is unspeakable and full of glory. This is what the psalmist calls upon the saints to do, in the beginning of the psalm; and so his end in composing it is answered;
because we have trusted in his holy name; that is, in himself, who is holy, just, and good; and so faithful to every word of promise, to every engagement of his, and therefore to be trusted in: and hence it appears that the joy before spoken of is the joy of faith.

his holy name--(Compare Psalm 5:12; Psalm 22:22; Psalm 30:4). Our faith measures mercy (Matthew 9:29); and if of grace, it is no more of debt (Romans 11:6).