Substitution.Christ's penal substitutionary death on the cross achieved many, many, many great things. Everything good we see in the world in fact. Every lovely sunset, every good moment with our friends, every answered prayer, every spiritual blessing...it all comes from the cross. Jesus' work was all satusfying, all encompassing, and all sufficient.
Christ's death on the cross provided a substitute for us in two ways, one of which is controversial, one of which is probably less so. Both of them are hugely important and fantastic news. In both of them Christ has become the once for all, final, satisfying substitute for us, in a way that lambs and goats never could be. Two of my favourite verses, both written by John describe Jesus put Him in these terms. He is '
the Lamb of God who takes away the sin of the world' and '
the Lamb, looking like he had been slain'. Throughout the Old Testament, from the time when Abraham was told to sacrifice Isaac, sheep and goats have been used as a sacrifice to God for human sin. Animals are killed, blood is shed and the sin is dealt with. But it leaves the question, what sort of God is happy with the blood of an animal to deal with the sins of people? What sort of God thinks of animals as a decent substitution for people? Surely there must be another plan, a better way?
Expiation.
In Leviticus 16:21, Aaron is told to lay his hands on the live goat, confess on it all the sins and iniquities of Israel and send it off into the wilderness to die. This goat them symbolically carries the sin of Israel against God far away from it. This animal had sins laid onto it, it is deserted and then goes off and dies. The cross, as Liam Goligher says, is Jesus fulfilling this picture and experiencing that abandonment. God is removing the problem of our sin by Jesus taking it out of sight. And because of this God will never again feel wrath for us, or punish us for our sins. They have been removed from us. God is now working all things together for the good of those who love Him. Our sin has been removed. It had to be done by a perfect, humna sacrifice, not by an animal. What sort of substitute is a goat for a man? This is why Jesus' deity and virgin birth are so important. No virgin birth means that Jesus is born into the line of Adam and therefore, like us all, imputed with his sin. No deity means that Jesus is incapable of living a sinless life, and therefore not a satisfying sacrifice for the Lord.
Propitiation.
This doctrine is the best bit of the Bible. The one we must fight for. One of the first 'hills to die on', as Mark Driscoll said. His first 'hill to die on' is the Bible but i guess this is much the same. I don't think you can clearly and literally read the Bible and come away without the doctrine of propitiation. In Leviticus 16:15 Aaron is told to kill the goat that is the sin offering for the people. He's told to kill it, to shed it's blood. This is how our holy and righteous God feels about sin. Sin deserves death, the shedding of blood. This goat was to be killed for the sins of the people, because sin deserves death. Again though, how can a goat be killed for the sins of men? Surely only a man can die for the sins of men? On the day of atonement the High Priest had to first kill a goat for his own sins before he could move onto dealing with the sins of the people...so even the one doing the killing had to deal with himself first. Jesus was killed for the sins of the people, fulfilling the picture given on the day of atonement. He was sinless, so didn't have to deal with His own sin first. He brought with him no sin offering, he was High Preist and sacrifice all rolled into one. He bore the whole weight of God's right, holy, measure, justified wrath against sin on His shoulders. He died under the weight of that sin. He fulfilled the picture of the day of atonement. The day of atonement had to happen every year...Jesus' death was once for all time, we will never have to kill another goat, never have to suffer the penalty of our sins, never have to face the wrath of God. Jesus has taken is all. He bore it all, and died under it all. Now we only need to believe...what a small price to pay.
Jesus really was the Lamb of God who took away the sin of the world, He removed it from us, and bore its penalty. What a sufficient work. What an awesome God!