I Have Come to Do Your Will

David begins with a memory of rescue: "I waited patiently for the LORD; he inclined to me and heard my cry" (Psalm 40:1). He had been sinking — "the pit of destruction," "the miry bog," a place with no footing (Psalm 40:2) — and God reached down, drew him up, and set his feet on rock. The result is not only safety but music: "He put a new song in my mouth, a song of praise to our God" (Psalm 40:3). Rescue makes singers of the rescued.

But then David says something startling for a man of the old covenant, surrounded by an entire system of altars: "In sacrifice and offering you have not delighted... Burnt offering and sin offering you have not required" (Psalm 40:6). He is not abolishing the sacrifices; he is seeing to the bottom of them. What God has always wanted is not the blood of animals as a payment that placates him, but a heart that gladly bends to him: "I delight to do your will, O my God; your law is within my heart" (Psalm 40:8). The offering God desires is an obedient life.

And there is the trouble, if we are honest. We do not delight to do God's will; we delight to do our own and dress it up as his. The law we would like within our hearts keeps sliding to the edges. David sings the ideal, and even David does not fully keep it. The psalm reaches for a singer it has not yet found.

The New Testament tells us who that singer is. The letter to the Hebrews takes these very words and puts them in the mouth of Christ as he enters the world: "Sacrifices and offerings... you have not desired, but a body have you prepared for me... Behold, I have come to do your will, O God" (Hebrews 10:5–7). Where the whole sacrificial system had been a promissory note — real, but never final — Jesus is the payment itself. He is the one whose heart truly held the law, who delighted in his Father's will down a road that ran to Gethsemane and did not turn back: "not my will, but yours, be done" (Luke 22:42). The body God prepared for him he offered up, "and by that will we have been sanctified through the offering of the body of Jesus Christ once for all" (Hebrews 10:10).

This is why our standing before God does not rest on the wobble of our own obedience. It rests on his. The whole-hearted "yes" we could never sustain, he sustained for us, and it is counted ours. Our new song is not "look how I have delighted to do God's will"; it is "look at the One who did, in our place."

So the psalm's two halves meet in him. He was drawn up from a deeper pit than David's — up from the grave itself — and the steadfast love David trusted proved deeper still. And the new song passes to us, who "see and fear, and put their trust in the LORD" (Psalm 40:3), singing not of a debt we paid but of a will we could not do, done for us to the end.