John Calvin Commentary Hebrews 10:7

"Then said I, Lo, I am come (In the roll of the book it is written of me) To do thy will, O God." — Hebrews 10:7 (ASV)

In the volume or chapter of the book, etc. Volume is properly the meaning of the Hebrew word, for we know that books were formerly rolled up in the form of a cylinder. It is also not unreasonable to understand book as meaning the Law, which prescribes to all God’s children the rule of a holy life; though it seems to me a more suitable view to consider him as saying that he considered himself to be in the catalogue of those who are obedient to God.

The Law, indeed, commands us all to obey God; but David means that he was numbered among those who are called to obey God. Then he testifies that he obeyed his calling by adding, I come to do thy will; and this uniquely belongs to Christ. For though all the saints aspire to the righteousness of God, it is Christ alone who was fully competent to do God’s will.

This passage, however, should stimulate us all to promptly obey God; for Christ is a pattern of perfect obedience for this purpose: that all who are his may strive with one another in imitating him, that they may together respond to the call of God, and that their life may exemplify this saying, Lo, I come. To the same purpose is what follows, It is written, that is, that we should do the will of God, according to what is said elsewhere: that the end of our election is to be holy and unblamable in his sight (Colossians 1:22).