In the volume of the book it is written of me; in the book of the law, as the, Targum and Kimchi on Psalm 40:7 interpret it; and which may design the Bible in general, the whole book of the Scriptures of the Old Testament: so ספר, "the book", is used for the whole BibleF18, and it is saidF19, all the whole law, that is, all Scripture, is called מגילה, "a volume"; accordingly there are things written of Christ in all the writings of the Old Testament, in the law, and in the prophets, and in the psalms. Jarchi interprets it of the law of Moses, and so it may design the pentateuch, or the five books of Moses; and there are several places therein, in which it is written of Christ, and particularly in Genesis, the first of these books, and in the head, the beginning, the frontal piece, the first part of that book; namely, Genesis 3:15 which may be principally designed. Books were formerly written in rolls of parchment, and hence called volumes; See Gill on Luke 4:17, See Gill on Luke 4:20. The end of his coming is next expressed by him,
to do thy will, O God; which, when he came, he set about with the utmost delight, diligence, and faithfulness, in preaching the Gospel, performing miracles, doing good to the bodies and souls of men, and in finishing the great work of man's redemption, which was the main part of his Father's will he came to do; and which he did, by fulfilling the law in its precept and penalty; by offering himself a sacrifice to God; by suffering death, the death of the cross; by destroying all his and our enemies, and so working out everlasting salvation."
Gill, John. "Commentary on Hebrews 10:7". "The New John Gill Exposition of the Entire Bible". https://www.studylight.org/commentaries/geb/hebrews-10.html. 1999.