The author of Hebrews had just pointed out that, despite all the animal sacrifices offered up by the people of Israel over the centuries, "it is not possible that the blood of bulls and of goats should take away sins" (Hebrews 10:4). That would require the once-for-all offering of "the Lamb of God, which taketh away the sin of the world" (John 1:29).
But that perfect Lamb could be none other than God Himself, in the person of His Son, the Lord Jesus Christ. No ordinary man, however powerful or wise or morally upright he might be, could ever accomplish such a mighty task. Neither could an angel remove human sin from the world. Only God could do that, but He must also be a man in order to pay the death penalty for man's sins, then also defeat death and live forever with those who would receive Him as Savior. He must be both eternal God and perfect man.
For this mission, He must have a human body, but it must be a very special body, with no genetically inherited mutational blemishes and no inherited Adamic sin nature. Thus His great testimony: "A body hast thou prepared me."
The Greek word for "prepared" is a strong word, connoting something like "made perfect" in most of its occurrences. It is used only one other time in Hebrews, in the very next chapter. "Through faith we understand that the worlds were framed by the word of God" (Hebrews 11:3). This correlation assures us that God "prepared" the human body of His Son, to be placed in Mary's virgin womb with the same perfect wisdom and care with which He had "framed" the worlds. Both were made "very good," perfectly designed, created, and made to accomplish His great eternal plan. HMM http://www.icr.org/article/5956/