Christ in His human flesh, in the body that was prepared for Him at the incarnation, was willing to serve the purposes of God, that animal sacrifices be replaced by the offering of His body for the sins of God's people.
Hebrews recalls Christ's promise: Lo, I come (in the volume of the book it is written of me), I delight to do Thy will!
There are numerous passages in the Old Testament in which the Spirit of Christ prophesied His own incarnation, His sacrifice for our sin, His death, and His victorious resurrection.
The very first such promise is found in Genesis 3, when God promises the serpent his ultimate crushing defeat: I will put enmity between your seed and her seed. He will crush your head, and you will wound his heel.
One day, a Son would come who would crush the devil's head, and overthrow all the evil that Satan brought into this poor world. That Son would defeat sin and death itself for His dear loved ones!
Looking back after He arose from the dead, Jesus Himself explained those very same texts that were written in God's sacred word, to the saddened disciples on the road to Emmaus. He opened up His word to their crushed hearts, proving that His suffering and death had long been promised, unto their redemption!
But then, Christ had said to God, "I delight to do Thy will!"
That is, Christ delighted to come in human flesh, to sacrifice Himself, to take away our sin, and shut down the animal sacrifices that God took no delight in.
God does delight in Christ's sacrifice, just as Christ does Himself!
Christ is already filled with joy more than any other man who ever lived, for God has anointed Him with the oil of gladness above all other men!