One could argue the first sacrifice was the animals which provided Adam and Eve with clothing. This happened right after the first sin (disobeying God, not trusting Him, eating the forbidden fruit). That animal skin, which meant the death of an animal, was used to “cover” the sin. That’s what the atoning sacrifices in the Old Testament were for - a covering.
Later, when God made his contract (which was more than just the signed agreement “contracts” are today) with Abram, the penalty for violations was blood and death. But, if that specific covenant’s agreement is studied, God is the one who pays the price if Abram or his descendants violate the stipulations. After all, He is the one who passed through the bloody chunks of meat, taking on Himself the penalty - to be torn to bloody pieces.
Then Moses gets the specific details of what that agreement entails - the Ten Commandments, the stipulations and minutia of what it means, etc. The Hebrews (after some setbacks) agreed to abide by God’s Law. That made them His people.
Again, when the Hebrews finished taking the last of the major fortifications in the Promised Land, Joshua lead them in a pledge to uphold God’s laws. The entire nation of Israel agreed.
Time after time through Judges and Kings, Israel turned away from God. Time after time the prophets warned them to turn back. All along the Hebrews were giving sacrifices. But it did no good.
Why? Because the sacrifice was the price for sin, but the penitent heart is what made it acceptable. If Israel had actually BELIEVED what was going on, they wouldn’t have turned to false gods. But in a part of the world which depended on rainfall for people to survive, it was easy to try appeasing a “god” who was in charge of the weather, rain, wind, etc.
Could it be Cain lacked a penitent heart? Perhaps Abel really believed in God and Cain was dismissive. “Yeah, I gotta do this ‘cuz Dad said.” That’s not the only theory about why God didn’t accept Cain’s sacrifice. Entire sermons have been preached on that particular point.
It’s said that God loves a cheerful giver. That doesn’t mean we shouldn’t give if we’re not cheerful. It means we have the opportunity to demonstrate God’s love by what we give - be it to church, various missions, or the beggar asking for a quarter. When we give we should be glad we have enough to give.
SIDEBAR: When the disciples asked Jesus why “this man” was blind, Jesus said it was to glorify God. That’s exactly why we should give, because God arranged for us to have the opportunity to show God’s glory.
So let me connect some dots.
Adam and Eve sinned, and God killed an animal to cover the sin. God and Abram made a covenant that all sin demanded death and dismemberment. God told Moses that the nation of Israel was required to follow His law. Joshua and the whole nation of Israel agreed they would follow God.
They failed.
The loophole is that God said He’d pay for our shortcomings.
Jesus, who is God, paid the wages for our sin. But His sacrifice did more than “cover” our sin. He “redeemed” us from sin, paying the price according to the God/Abram covenant.
All we have to do is sign the contract and turn to Him, away from other “gods.”
Then we’ll be God’s people, just like when the Hebrews agreed to His law.
