What do you think of when you hear the word duty? Many of us would likely think of something we have to do but do not want to do. “Do your duty,” we have been told, often by people who know that our heart is not in doing what we are supposed to do. Many of us also think of duty as something that is owed. That can make the prospect of doing one’s duty even less appealing. Most of us don’t like owing anything to anyone.
Scripture abounds with the notion of duty. For instance, the Ten Commandments are set up as laws that the Israelites had to obey because God had redeemed them from slavery (Ex. 20:1–17). The structure of many of the New Testament Epistles is similar. In a book such as Romans, there is first a recounting of all of the things Christ has done for us (Rom. 1–11) and then several chapters of ethical instruction (chaps. 12–16). The implication is that we have a duty to live according to those ethics because of Jesus’ work in our behalf.
Certainly, the Word of God would have us do our duty regardless of whether we feel like it, but one of the wonderful blessings of our Lord is that He makes our duties into delights. That is one of the lessons we can learn from today’s passage. We see in Psalm 149 that we are to “rejoice” in our King (v. 2). We are to take great joy in Him, our Lord and Maker. This is not optional. It is commanded and given to us as one of our duties.
Yet the Lord would not have this be a matter of drudgery. It would have been enough simply for Him to order us to rejoice and be done with it. However, that is not what He does in today’s passage. He provides us with good reasons to find our joy in our Creator. We read, for example, that “the Lord takes pleasure in his people” (v. 4). The all-sufficient God, who has no need of anything outside of Himself to be content and to enjoy a perpetual state of bliss, has chosen to find His pleasure and joy at least partly in those whom He has saved. There could be nothing more wonderful than that. Moreover, the Lord has granted us to share in His work. Though we are unworthy, we will take part in God’s execution of His vengeance (vv. 6–9). Surely, it is cause for us to rejoice that we will share in the Creator’s work.
God commands us to rejoice in Him and gives us the reason and power to do so. In his sermon “Jubilee Joy—or, Believers Joyful in Their King,” C.H. Spurgeon writes that God “would have His people happy and, by His Grace, He makes them so! We rejoice in our King because our King makes us rejoice! . . . Blessed religion, in which happiness has become a duty!”