The Bible tells us that the price for sin is death. We are not talking about our bodies dying and getting buried. We are talking about our souls. When God breathed life into Adam, he became a living soul. This is what separates us from the rest of the world. This is what makes us higher than the animals. We have a piece of God inside of us that the rest of creation does not have. The separation from God that is caused by sin means the soul has to die. The Bible speaks of the "second death" this is where the soul is thrown into the "lake of fire."
It is sort-of like we are God's fingers and toes. The fingers and toes have a really bad infection called sin. God is not going to let this infection kill Him, so He will cut off His fingers and toes and burn them to stop the infection.
But there is another way!