The festivals and feasts of ancient Israel were corporate expressions of the individual joy and piety that all of God’s people should have. Expressions of this piety took a variety of forms — prayer, Scripture study, music, and more. The book of Psalms was especially important, for these hymns were sung as people went up to Jerusalem for the festivals, and they were also used as a guide to private worship.
Music was clearly an important part of worship — both public and private — during the old covenant. The great acts of the Lord’s deliverance, such as the exodus, were celebrated with song (Ex. 15:1–21). Numerous psalms speak of praising God with instruments of every kind (Pss. 92:1–4; 150). Indeed, there is much that could be said about music, for it has not passed away in the new covenant and continues to be an important part of the worship of our redeeming Lord.
Today’s passage is one of many in the Old Testament that expresses the worshiper’s dedication to sing the praises of God. Here David sings of both God’s love and His justice (Ps. 101:1), which is instructive for how we are to properly worship. Songs that we sing to the Lord are to emphasize His attributes and His great deeds; in other words, the content of our songs is very important. Scripture may have little to say directly about the style of music used in worship, but it is insistent that the words we sing be God-centered and filled with His truth.
David’s song is the response of a converted person to the Lord’s magnificent qualities, and it says something about the multifaceted nature of the divine character. He marvels, as Augustine comments, that “God neither loses the severity of judgment in the bounty of mercy, nor in judging with severity loses the bounty of mercy” (Nicene and Post-Nicene Fathers 1:8:491). Our songs should rejoice in the breadth of the Lord’s attributes, and all believers who are able should be unafraid to praise Him with all their might during times of song.
Finally, the music of worship is the music of the covenant. The remainder of Psalm 101 expresses David’s commitment to his covenant with God — he will be loyal to fulfill the obligations of the righteous king of Israel (vv. 2–8; see Deut. 17:14–20). When we sing to the Lord in worship, we are likewise committing to keep His covenant.