The Book of Hebrews offers an extended discourse on the early Christian belief that Jesus on the cross was the ultimate and perfect sacrifice for the sins of humanity. Hebrews 9:13-14 sates, "(13) For if the blood of goats and bulls, with the sprinkling of the ashes of a heifer, sanctifies those who have been defiled so that their flesh is purified, (14) how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to worship the living God!" (NRSV)
For many in the 21st century, including some Christians at least, the doctrine of "substitutionary atonement" is off-putting for its emphasis on blood and violence and is difficult to understand even as it reflects ancient ways of thinking otherwise long fallen out of favor. Indeed, it is cruel to take an animal, force it on an altar, and take its life in the midst of an assembly of people hoping that its death will give them salvation. The cross was cruel, and according to modern sensibilities we cannot take glory in it or see in it God's will from the beginning of creation. We can and do still insist that Jesus died because of our sins and even for them, but not as a sacrificial lamb slaughtered to please God's justice (as one theory of substitutionary atonement would have it). We don't think like that anymore—thankfully not.
Let us not, however, throw the baby out with the bathwater. While the doctrine reflects ancient religious practices long fallen out of favor among the vast majority of the world's peoples, it still was built out of important theological insights that remain important to us today. It most especially affirms that God loves the world and not only cares about it but is impacted by its pain and suffering. God cares. God is involved, furthermore, in bringing healing out of the vast wellsprings of pain. God's Spirit is working for the emergence of the Kingdom.
The death of Christ on the cross, according to Hebrews 10:11-18, furthermore, brought all other forms of sacrifice to an end. That is, in ancient times, Christians did not participate in the bloody acts of religious sacrifice common to their day. They believed that except for Christ the practice of sacrificing animals on altars was senseless. In our time, we need but extend that insight to include the death of Christ as well and to affirm that in our own understanding of God's love for humanity there is no room for God sacrificing anyone on a cross. Jesus, rather, marked a seminal moment in God's ongoing struggle with the human heart, so important for us as Christians that we see in and through Christ the deepest expression of God's love known to us. He was for us the Son of God. The cross was an intimate and essential element in the "Christ-event". Without it there would have been no resurrection, which for us as Christians is the real heart of the good news of our faith. Amen.