Christian redemption dogma claims that Jesus's death is a human sacrifice made to God in the same way that animal sacrifices were made. It is said to be a special sacrifice in that while animal sacrifices atone for day-to-day sins, a human sacrifice is needed to mitigate the Original Sin passed down from Adam. The saving of other people by dying on a cross is the propitiation of Original Sin and thus making the person's soul suitable for Heaven.

That's the short answer. The concepts have numerous problems in many dimensions. Some of the problems are fact-based and thus falsify and invalidate the whole scheme, albeit indirectly.

Can I bruise myself for my mortgage payment?

Seems like that primitive impulse to punish someone, anyone, when things don't go your way. Way to go, God.

Damn good question, that I've always wondered about myself. What the ....???