Hebrews 10:4 states that the blood of bulls and goats cannot atone for sin. To those familiar with the argument of Hebrews or the typology of sacrifice in the Bible, it will come as no surprise that an animal cannot atone for the sins of a human. The Old Testament sacrifice can only purify the flesh, and only for a time. The value of an animal is insufficient for ransoming men made in the image of God. Only another man can do that, but then only if that man is unblemished in body and will.
Writing about the mind of Christ in Philippians 2, Alec Motyer makes this point extremely well (see his commentary, The Message of Philippians, 117). Pointing to Isaiah 53, he observes that the sacrifice that takes away the sin of the world must of necessity be perfectly willing. Animal sacrifices are not only unable to atone for sin because of their deficient worth, but also because an animal does not volunteer itself for the sacrifice. Moyter writes,
All through the long years of animal sacrifice the Lord had driven home the lesson that in the divine purposes there could be a transference of sin and guilt from the head of the guilty to the head of the innocent. Whenever a sinner brought his animal to the altar and laid his hand on the beast’s head the lesson was plain: this stands in my place; this bears my sin. Yet the substitution was incomplete, for the central citadel of sin, the will, was left unrepresented in the uncomprehending, unconsenting animal. Isaiah foresaw that only a perfect Man could be the perfect substitute and that at the heart of this perfection lay a will delighting to do the will of God (cf. Ps 40:6-8; Heb 10:4-9).
Praise God for the man Jesus Christ, who voluntarily took on the form of a servant, humbling himself to the point of death, even death on the cross. In his perfect sacrifice, he not only offer an infinitely worthy sacrifice; he also volunteered his will to die in the place of his sheep. In this, the message of penal substitution acknowledges the personal, willing sacrifice of the perfect Son, who in turn is leading his redeemed into the Lord’s eternal pastures.
Soli Deo Gloria, dss