Cain, the eldest son of Adam and Eve, was born after they were banished from the Garden of Eden. He was a farmer, a tiller of the soil. Cain and his brother Abel brought offerings before God.
God accepted the offering of Abel, but rejected Cain's. Angered by this rejection, Cain killed his brother, for which he was subjected to a double curse: The ground would no longer yield to him its wealth, and he was condemned to be a fugitive and a vagabond for the rest of his life.
God put a mark on Cain, so that no one who would come upon him would kill him. Cain settled in the land of Nod, east of Eden. Cain established a city and named it after his son Enoch (Genesis 4:1-17).
In the New Testament, Cain is seen as the opponent of his righteous brother Abel (Hebrews 11:4), as a symbol for an evil way of living (Jude, verse 11), and as someone whose works were wicked (1 John 3:12).
The famous saying "Am I my brother's keeper?" is said by Cain when the Lord asked him "Where is your brother Abel?" (Genesis 4:9).