By faith Abel offered to God a more acceptable sacrifice than Cain, through which he was commended as righteous, God commending him by accepting his gifts.

Hebrews 11:4

Very often, the New Testament gives us the key to understanding an Old Testament story, and the New Testament tells us quite clearly that the difference between Cain and Abel was faith.

Cain was a man without faith. He came with his family to worship God. He even brought offerings to God. But he did not have faith. Faith is trusting in and acting on what God has revealed.

God had already revealed that the only way we could come to Him was on the basis of a sacrifice that involved the shedding of blood. Although this was revealed more fully to Moses later, the principle of a sacrifice involving death goes all the way back to the Garden of Eden. When Adam and Eve sinned, they lost their innocence and they knew they were naked. Then we are told, “The LORD God made for Adam and for his wife garments of skins and clothed them” (Gen. 3:21).

You can’t make garments of skin without killing an animal. So, it is quite clear that God killed an animal on the very day that the first sin was committed. God shed blood in the Garden of Eden. The very first sacrifice that was ever made was offered by God.

Cain and Abel would have learned this from their parents. “Our sins lead to death, but God is gracious, boys. He has allowed that another will die in our place. He will accept the sacrifice of a lamb, and He will show you mercy. That’s how you find peace with Him.”

Abel believed God’s promise and he acted on it. But Cain wanted to offer something he had worked on. That’s why he brought the fruit. That was his problem. He was a man without faith.