Man’s sin and rebellion against God caused a separation between man and God. Man could no longer live so close to God. Therefore, Adam and his wife were sent out of the garden of peace as a judgment against sin.
And the LORD God said, “The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.” So the LORD God banished him from the Garden of Eden to work the ground from which he had been taken. After he drove the man out, he placed on the east side of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life. Genesis 3.22-24
The man and woman began having children. It was not long before the sinfulness that had entered the world began to destroy their children as well. The firstborn son was Cain, who learned to farm the land. The second son was Abel, a keeper of animals. God told each of Adam’s sons to honor him by bringing a sacrifice to him. God accepted Abel’s offering because Abel brought God the best of his animals. However, God rejected Cain’s sacrifice because of Cain’s pride. Cain became jealous and angry at his brother Abel, so he killed him. God confronted Cain with this sin and cursed him, saying:
“What have you done? Listen! Your brother’s blood cries out to me from the ground. Now you are under a curse and driven from the ground, which opened its mouth to receive your brother’s blood from your hand. When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth.” Genesis 4.10-12