Hebrews 10:5

When he cometh. That is, at the time of the incarnation. Christ is represented as uttering the words of Ps. 40:6-8 at the time of His entrance into the world. The preexistence of Christ is here clearly implied.

Sacrifice and offering. The statement that God did not desire these apparently has reference to the offering of these sacrifices merely as a fulfillment of a ritual requirement without true devotion of heart. It was Christ who instituted the sacrificial system. Properly used, it would have brought a blessing to the conscientious worshiper. But God found no pleasure in the sacrifices of the insincere worshiper (see 1 Sam. 15:22; Hosea 6:6).

A body hast thou prepared me. This is the reading of the LXX. For the reading of the Hebrew and its significance see on Ps. 40:6. The writer of Hebrews was doubtless aware of the two readings, and of the two he chose that of the LXX. The wording of the LXX taught a significant truth, and his use of that reading gives an endorsement to the truth taught without necessarily endorsing the translation as being a faithful representation of the Hebrew.

For the meaning the author gives to “body” see on v. 10.