1 John 2:2
 He is the propitiation for our sins, and not for ours only but also for the sins of the whole world. (ESV)
We tend to struggle with the idea that God is at times a wrathful, vengeful God. We want to delete those portions of Scripture that speak of his judgment and focus on the passages that talk of his mercy and love. And as a result we have a very unhealthy and inaccurate view of who God is. Many times I have heard people say that God is mean in the Old Testament, and nice in the New Testament.
As we look at this word propitiation in 1 John 2:2 it will help us come to a more balanced understanding of just who God is. We will go to the great late Dr. R.C. Sproul for a little help on this one:
"The prefix pro means “for,” so propitiation brings about a change in God’s attitude, so that He moves from being at enmity with us to being for us. Through the process of propitiation, we are restored into fellowship and favor with Him. In a certain sense, propitiation has to do with God’s being appeased."
- R.C. Sproul, www.ligonier.org
So, let's put it together. God is justifiably angry at our sinful nature and behavior. Because he is perfectly just and holy he intends to bring wrath and punishment to us for our sin. But, Jesus' sacrifice on the cross steps in the way of that wrath. Jesus takes the wrath that was intended for us and receives it onto himself. This is why he suffered. He suffered to take the wrath we should have received, and as a result God the Father can now look upon us with favor, instead of wrath. God's righteous wrath is not ignored, it is placed on Jesus.
Another way we can understand propitiation is to interpret it as "payment." He payed for our sin. John tells us that he is the propitiation for our sins and also the sins of the whole world. Does that mean every person who ever lived? No. It means, he paid for the sins of all who would believe in him. Sadly, those who do not place their faith in Jesus Christ will have to eternally pay for their sin.
What a wonderful Savior we have. He is the propitiation, or payment, for our sins. Take some time today thanking him for his amazing gift of love for us.