Psalms 40:7 Commentary: The Scroll and Christ's Willing Obedience

Ancient books were not bound like modern volumes. They were written on sheets of papyrus or vellum, sewn together and rolled around a wooden rod. The Hebrew term megillah (scroll) and the Latin volumen describe this format. Adam Clarke describes a Torah scroll of his day that was two feet wide and over a hundred feet long, requiring a table to manage. In David’s time, around the tenth century BC, the only “book” that would have existed in written form was the Law of Moses (the Pentateuch). The Psalms often refer to God’s law as a guide for life, and here the speaker refers to a specific written record that speaks of him.

The context of Psalm 40 is a song of thanksgiving after deliverance. In verse 6 the psalmist declares that God does not desire sacrifice and offering; instead “you have opened my ears”, an idiom for making someone receptive to God’s will. The phrase “Then I said” in verse 7 signals a response to that divine instruction. In the ancient Near Eastern court, when a servant heard the king’s command, the proper reply was “Here I am, I come.” The “scroll of the book” thus represents the written will of God, the covenant obligations and promises recorded in the Torah. The speaker says that this written record already contains a prescription or prophecy that applies to him.

The consulted sources note no significant textual variants for Psalm 40:7. The Hebrew text is consistent across manuscripts, and the Greek of the Septuagint (which the author of Hebrews follows closely) reads “ἐν κεφαλίδι βιβλίου” (“in the volume of a book”), matching the Masoretic Text. The quotation in Hebrews 10:7 differs slightly in wording but maintains the same sense. No manuscripts of sufficient weight suggest an alternative reading.

The earliest explicit reception of this verse is its quotation in the Epistle to the Hebrews (likely late first century AD), where it is placed on the lips of Christ at His incarnation. The writer uses it to argue that Christ’s once-for-all sacrifice supersedes the Levitical system. Early church fathers such as Justin Martyr and Athanasius cited Psalm 40:7 as a prophecy of Christ’s willing humanity. During the Reformation, Calvin and other expositors read it primarily as David’s personal testimony, while confessional documents like the Westminster Larger Catechism treated it as messianic. In hymnody, lines like “Lo, I come” have been adapted into hymns of dedication (e.g., “I Am His, and He Is Mine”). Modern scholarship generally affirms a christological reading, while acknowledging the original Davidic setting.

Three-point outline

1. The insufficiency of external religion: God does not desire sacrifice and offering apart from the heart (v. 6).
2. The response of the willing Servant: “Lo, I come”, the speaker offers himself in place of animals.
3. The scriptural foundation: This obedience is not an afterthought; it is “written in the scroll of the book” (the Torah prophecies).

Five-point outline

1. A problem stated: Animal sacrifices cannot take away sin (v. 6, cf. Hebrews 10:4).
2. A new response: The speaker says “Behold, I have come”, a voluntary, personal offering.
3. A divine appointment: The scroll of the book (the Law and the Prophets) already contains the plan.
4. A delight in God’s will: Verse 8: “I delight to do your will, O my God.”
5. A public testimony: The speaker proclaims righteousness in the great congregation (v. 9, 10).

Illustration hooks

• A signed contract: When someone agrees to take responsibility for a debt, they sign a document. Here the Messiah points to the existing “scroll” as the contract He came to fulfill.
• A rescue mission planned in advance: A firefighter trains for years before a single blaze. The plan for Christ’s obedience was written long before He came.
• A child’s “yes” to a parent’s request: The simple response “Lo, I come” echoes the trust of a son who says “I will go” even before knowing the cost.

Questions your congregation is asking

• Was King David speaking about himself, or did he look ahead to Christ?
• What does the “scroll of the book” mean, is it the entire Old Testament or just the Torah?
• How can I know if my obedience is merely external or a willing “I come” from the heart?

Psalm 40:7 sits at the center of a psalm of thanksgiving. The writer has just said that God does not desire animal sacrifices. Then, in a dramatic turn, the speaker says “Behold, I have come”, offering himself instead. The New Testament book of Hebrews quotes this verse and applies it to Jesus Christ. As you discuss this passage, consider how the Old Testament already pointed ahead to a greater sacrifice.

Discussion questions

1. Read verses 6, 8 aloud. What contrast does the psalmist draw between sacrifices and the speaker’s response?
2. The phrase “the scroll of the book” appears here and in a few other Old Testament passages. Based on the context, what “book” do you think is being referenced (Torah, the Psalms, a heavenly book)? Support your answer with the text.
3. How does the author of Hebrews (chapter 10:5, 10) interpret this verse? What does he say is the significance of Christ saying “I have come to do your will”?
4. In verse 8 the speaker says “I delight to do your will, O my God.” How does this attitude differ from merely obeying out of duty or fear?
5. If this psalm was originally about David (as the title suggests), how could it also apply to Jesus? What does it mean to read the Psalms as pointing to Christ?
6. Barnes and other commentators argue the verse “cannot with any propriety be applied to David himself.” Do you agree or disagree? Why?
7. How does the truth that Christ willingly came to do God’s will shape your view of salvation? Does it affect how you approach obedience in your own life?