I believe that the translators of the Septuagint realized that to bore the ears was to require the obedience of Christ, and Christ's obedience was mainly for Him to die on the cross. For Him to die on the cross, He needed a human body. Hebrews 2:14 says that because Christ was going to destroy Satan, He needed to partake of blood and flesh, that is, He needed a body. I believe that the Septuagint translators may have realized that "You have bored My ears" in Psalm 40:6 would not be understood by most readers so they translated it as "a body You have prepared for Me." To bore the ears was for Christ's obedience to die on the cross, and to prepare a body was also for His dying on the cross. Thus, both translations are with the same purpose. God prepared a body for Christ to come to do God's will to be God's unique sacrifice on the cross.

Psalm 40:7 says, "Behold, I have come," indicating Christ's first coming through His incarnation for the establishment of the new testament by Himself as the enacting sacrifice and offering.

Verse 7 also says, "In the scroll of the book/It is written concerning Me." This indicates that Christ was prophesied in the Scriptures of the Old Testament and that Christ will do God's will for the accomplishment of God's New Testament economy according to the Old Testament prophecies concerning Him.

When the Lord appeared to His disciples in resurrection, He told them all the things that were written concerning Him in the Scriptures (Luke 24:27). In Luke 24:44-45 He told the disciples, "These are My words which I spoke to you while I was still with you, that all the things written in the Law of Moses and the Prophets and Psalms concerning Me must be fulfilled. Then He opened their mind to understand the Scriptures." The Lord's word here unveils that the entire Old Testament is a revelation of Him and that He is its center and content. Our life-study of the Old Testament is full of interpretations and definitions of the types concerning Christ.

Psalm 40:8 says, "I delight in doing Your will." This indicates that Christ was willing to do God's will in His commission of His incarnation to fulfill and replace all the sacrifices and offerings of the Old Testament for the termination of God's Old Testament economy, so that He could initiate and establish God's New Testament economy (Matt. 26:26-28) for the producing and building of the church to be His organic Body, which will consummate in the New Jerusalem. When the Lord established His table, He indicated that His blood shed through His death was the enacting factor of the new covenant.

In Hebrews 10:5-9, after quoting this prophecy concerning Christ in Psalm 40:6-8, Paul commented that Christ coming to do God's will is to take away the first that He may establish the second (Heb. 10:9). "The first" in Paul's comment refers to the sacrifices and offerings of the first covenant, the old covenant; and "the second" refers to the sacrifice of the second covenant, the new covenant, which sacrifice is Christ. The commission which God committed to Christ in His first coming through incarnation was to put away the animal sacrifices of the old covenant and to establish Himself, in His body, as the sacrifice of the new covenant. This is to terminate God's Old Testament economy and to initiate God's New Testament economy, thus making the prophecy in Psalm 40:6-8 one of the greatest prophecies concerning the all-inclusive Christ.