Among its other purposes, the book of Psalms serves as the hymnbook for the people of God. Its contents reveal the kinds of prayers that please the Lord. These prayers are also intended to be sung. Psalm 100 is a hymn of thanksgiving and praise unto our Creator, and its call for the people to sing unto the Lord makes it a fine call to worship as well.
Remarkably, the psalm opens with a call for all the earth to “make a joyful noise to the LORD” (v. 1). Because the Old Testament is so concerned with the history of God’s relationship to ancient Israel, it can be easy for us to assume that the ancient Israelites had no real concern for the salvation of the nations around them. Without a doubt, the prophets do condemn Israel for being a poor witness to the Gentiles, for not fulfilling her call to be a servant and light to the nations (Isa. 42:18–25). Nevertheless, there were always people in the old covenant community who sought to bring the worship of the one true God to the nations.
This is confirmed in Psalm 100:3, which states, “Know that the LORD, he is God!” In our English translations of the Old Testament, the Hebrew name Yahweh, which is the special covenant name of Israel’s covenant Lord, is typically rendered using small caps: “LORD.” To paraphrase, then, verse 3 is a call to the nations to understand that the Lord of Israel alone is God, that the Lord of Israel is not ruler over just that nation but is the only true God, the Creator of all. The Lord who has revealed the Scriptures treasured by the ancient Israelites is the only God. All people belong to Him by right, and those who will trust and believe in Him will belong to Him as His treasured possession. They and they alone will be His children (Deut. 7:6; John 1:11–13).
In calling for the whole earth to “make a joyful noise to the Lord,” the psalmist also exhorts Israelites and non-Israelites alike to “serve the Lord with gladness!” Those who have come to know the Lord God Almighty are His servants, but this is not a service of drudgery. Augustine of Hippo, in his sermon on Psalm 100, writes, “Fear not the servitude of that Lord: there will be no groaning there, no discontent, no indignation; no one seeketh to be sold to another master, since it is a sweet service, because we are all redeemed.” To be a servant of the Lord is to hold a high and enjoyable calling. It is service to the One who never mistreats His servants but rather accepts them into His family.