One of the threads that runs through the Scriptures is the ritual of sacrifice. Abraham did it on the mountain. Israel did it at the Temple. Jesus did it at the Cross, where He is called the "Lamb" of God.
This seems strange to us on this side of the Gospels. It looks a lot like some of the sacrifices that other religions offered to their so-called gods. We aren't really sure what to make of this practice, where it came from, why it was important. God even says at a few points in the Old Testament that He's not satisfied by the animal offerings; it's not what He really wants from His people.
So then, what's up?
It looks like a very human thing to do in an agrarian society. You want to offer something to your God, so you offer Him something that you have - livestock. You want to figure out how to offer it to Him, so you offer it by fire. You cook it for Him. You take the time to slaughter it carefully, to cut out the choicest parts, to remove all the stuff that isn't the best, and to give Him the most worthy part of it.
This is how our brains works.
Certainly, I think, it's how Cain's brain worked. Abel's, too, really, but he didn't offer livestock.
When we go back through Genesis, we catch this story of offerings to God pretty early. Abel, who worked the land, offered the best of his crops. Cain, who tended livestock, offered the best of his herds. Each man brought to God what he had, the things that he invested himself in every day.
Of course, God accepted the crops from Abel, but rejected the animal from Cain. This led Cain into a fit of jealous rage, and he killed his brother.
This doesn't, then, seem like a people who would end up sacrificing animals to the Lord. The first time it happened, that sacrifice was rejected and it resulted in creation's first murder. (Unless you count the slaughter of the animal itself as murder....)
But we cannot ignore that just a few chapters later, Abraham is ordered to sacrifice his son, then given a ram in the bushes instead. Abraham sacrifices this animal in thankfulness to God, and the whole thing is changed. God actually starts commanding His people to bring Him livestock.
So how do we get from a rejected offering to a commandment for ritual sacrifice? Why does God reject Cain's offering? Why does He accept Abraham's? Why does He tangle a ram in the bushes in the first place? And why, then, does He command His people to bring Him livestock?
So let's start here: Cain's offering wasn't the first animal sacrifice in the Scriptures. Actually...