4. And I will go to the altar of God. Here he promises to God a solemn sacrifice, in commemoration of the deliverance which he should obtain from him; for he speaks not only of the daily or ordinary service, but in making mention of the altar on which it was customary to offer the peace-offerings, he expresses the token of gratitude and thanksgiving of which I have spoken. For this reason, also, he calls God the God of his joy, because, being delivered from sorrow, and restored to a state of joy, he resolves to acknowledge openly so great a benefit. And he calls him the joy of his rejoicing, that he may the more illustriously set forth the grace of his deliverance. The second word in the genitive is added by way of an epithet, and by it he signifies that his heart had been filled with joy of no common kind, when God restored him, contrary to the expectation of all. As to the fifth verse, I have already treated of it sufficiently in the preceding psalm, and therefore deem it superfluous to speak of it here.