These verses, which seemingly deny the need for sacrifice as a means of salvation, really illustrate the need for the death of Jesus on the cross. F.F. Bruce, writing about these verses, sees the Old Testament sacrifices as requiring the “obedient heart” and Christ offers that “wholehearted obedience.” Quoting J. Denny’s The Death of Christ, Bruce writes, “Our author’s contrast is not between sacrifice and obedience, but between the involuntary sacrifice of dumb animals and ‘sacrifice into which obedience enters, the sacrifice of a rational and spiritual being, which is not passive in death, but in dying makes the will of God its own.’” 
Bruce goes on to explain that while it was the Father’s will for Jesus to die, “it was also His own spontaneous choice.” Elaborating further and once again quoting Denny, he writes:
"It is the atonement which explains the incarnation: the incarnation takes place in order that the sin of the world may be put away by the offering of the body of Jesus Christ.” The offering of His body is simply the offering of Himself; if here sanctification and access to God are made available through His body, in verses 19 and 29 they are made available through His blood. Whether our author speaks of His body or His blood, it is His incarnate life that is meant, yielded to God in an obedience which was maintained even to death. So perfect a sacrifice was our Lord’s presentation of His life to God that no repetition of it is either necessary or possible: it was offered “once for all.Bruce and Denny’s commentary are important in light of the attacks occurring on the theology of atonement and in the context of religious evil. First, God’s desire for Old Testament people is not different than His desires for New Testament people.
His desire is that sacrifice be made with a willing heart; the desire to obey God is all-important. In the Old Testament the willing heart was bound-up with the sacrificial animal. However, only Jesus Christ could offer that perfect willing obedience. He made the perfect sacrifice and was the perfect sacrifice.
To eliminate Jesus as sacrifice on the cross is also to destroy the theology of the Old Testament. Christ’s death on the cross was not just the Father’s will it was the “spontaneous choice” of Jesus Christ. Atonement theology is infused with the doctrine of the Trinity. To redo or give up the meaning of the atonement tends to eliminate the Trinity.
The understanding that “the atonement explains the incarnation” clarifies the biblical understanding of God’s purpose in the incarnation. If a theologian says that for our salvation the incarnation “would be enough,” but fails to acknowledge the redemptive purpose of the cross he simply does not understand the biblical view of the incarnation. The biblical statements of the purposes of God concerning the incarnation are very clear.
Peter’s first sermon emphasizes the purpose and meaning of the incarnation in the death of Christ on the cross. “This Man, delivered over by the predetermined plan and foreknowledge of God, you nailed to a cross by the hands of godless men and put Him to death.” (Acts2: 23) Furthermore, Paul writes to the Colossians:
For it was the Father’s good pleasure for all the fullness to dwell in Him, and through Him to reconcile all things to Himself, having made peace through the blood of His cross; through Him, I say, whether things on earth or things in heaven. (Colossians1: 19-20)The final important note is that the sacrifice is “once for all.” This also speaks about the God of the Old Testament, who is of course the compassionate God of the New Testament. His grace of redemption covers all of the scripture, both old and new. The scripture confirms all of this:
 Ibid, 235.
Picture by Stephen Larson