In contrasting the sacrifice of Jesus with that of the blood sacrifices offered under the old covenant, the Hebrew writer quotes from Psalm 40:6-8, establishing it as a Messianic prophecy.
As seen in the preceding verses, God did not intend or desire for the animal sacrifices under the previous covenant to continue. They were insufficient to deal permanently with sin. Each year the offerings were continued.
God’s purpose was to send His only begotten Son into the world, Jesus, to offer up Himself as that efficacious sacrifice for sin. Jesus did God’s will. He proclaimed from the beginning of His life (Luke 2:49) until the end of His life (Matthew 26:39) that His purpose on earth was to do the will of His Father in heaven. In so doing, His sacrifice accomplished the change in the covenants, as the new will was ratified by His shed blood.
It is also that blood that finally cleanses us, separating us in holiness to God. Because sin’s debt has been paid, Jesus’ sacrifice was “once for all.”
