5 Therefore, when He came into the world, He said: “ Sacrifice and offering You did not desire, but a body You have prepared for Me.
6 In burnt offerings and sacrifices for sin You had no pleasure.
7 Then I said, ‘Behold, I have come — in the volume of the book it is written of Me — to do Your will, O God.’”
8 Previously saying, “Sacrifice and offering, burnt offerings, and offerings for sin You did not desire, nor had pleasure in them ” (which are offered according to the law),
9 then He said, “Behold, I have come to do Your will, O God.” He takes away the first that He may establish the second.
10 By that will we have been sanctified through the offering of the body of Jesus Christ once for all.
The quotation (v.5) is taken from the Septuagint (Psalm 40:6-7) and, at first sight, appears to fail to express the Hebrew. In Hebrew the last clause reads: “mine ears has thou opened.” Though “body” is used here instead of “ears,” neither the Septuagint nor the author of Hebrews should be regarded as corrupting or even weakening the meaning of the Hebrew. Rather, they heighten its meaning. And synecdoche is being used, that is, the substitution of a part for the whole. The use of the ears for the body is fitting here, since the context involves the hearing of and obedience to the will of the Father. Ears require the reality of a body. — KJV Commentary, page 1698.
The writer of Hebrews can’t be thought to be denigrating the Levitical system — he uses a quote from David to support his point.
burnt offerings (v.6) — those that were entirely burnt up on the altar
God ordained the Old Testament sacrifices, and in His forbearance, accepted them, but they could only cover sin, they could not pay for it and so God took no pleasure in them (v.6).
in the volume of the book (v.7) — The Old Testament contains instruction for the Messiah in accomplishing God’s will.
Not only did the Lord declare that He had come to do the Father’s will, He also showed how inseparable were His own person and work from the testimony of Old Testament Scripture. He had come to fulfill both the Law and the prophets (Matthew 5:17). He was the one great subject of their testimony (John 5:39). What He taught His disciples before His death He repeated after His resurrection, “that all things must needs be fulfilled, which are written in the Law of Moses, and the prophets, and the Psalms concerning Me” (Luke 24:44). So when He says, “Lo, I come to do Thy will, O God,” He declares in the same breath, “In the roll of the Book it is written of Me.” — Hebrews, by W.E. Vine, pages 300-301.
previously saying (v.8) — referring back to verse 5
sacrifice (v.8) — peace offering
offering (v.8 — first usage) — meal offerings — All four offerings of Leviticus 1-7 are mentioned here.
will (v.10) — the will of God which Messiah came to do and which the Old Testament sacrifices could not do
sanctified (v.10) — set apart for God
once for all (v.10) — emphasizing the completeness of Christ’s sacrifice contrasted with the repeated Old Testament sacrifices
It [this passage] argues that the Son’s offering of Himself is the true and final offering for sin, because it is the sacrifice, which according to prophecy, God desired to be made. — Hebrews in the Greek New Testament, by Kenneth S. Wuest, page 174.