“If a man acts intentionally to cunningly murder his neighbour; from My Altar take him to die.”
~ Exodus 21:14
As far as actions with negative effects go, murder is about as bad you get. As such, it’s not outrageous that Judaism advocates the death penalty.
But what’s God’s Altar got to do with it?
People who’ve done damage in the world usually regret their mistakes and often turn to religion for atonement. While this may be helpful on a personal level when sincere, it doesn’t clean-up the mess they made.
So God says: ‘First take responsibility, then we’ll talk’.