Then will I go unto the altar of God - The altar on Mount Zion, where sacrifices were offered: 2 Samuel 6:17. The meaning is, that he would again unite with others in the public and customary worship of God. Compare the notes at Psalms 42:4.
Unto God - Into the immediate presence of God; the place where he was worshipped.
My exceeding joy - Margin, the gladness of my joy. The Septuagint renders this, “who makes my youth joyous:” or, “the joy of my youth,” (Thompson) The Hebrew is, the gladness of my joy; meaning, that God was the source of his joy, so that he found all his happiness in Him.
Yea, upon the harp will I praise thee - Compare the notes at Psalms 33:2-3. Instruments of music were commonly used in the worship of God, and David is represented as excelling in the music of the harp. Compare 1 Samuel 16:16-23.
O God, my God - It was not merely God as such that he desired to worship, or to whom he now appealed, but God as his God, the God to whom he had devoted himself, and whom he regarded as his God even in affliction and trouble. Compare the notes at Psalms 22:1.