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. Abel was a shepherd. Cain and his brother Abel brought offerings before God.
God accepted the offering of Abel, but rejected Cain’s. This rejection made Cain jealous and angry so he killed his brother for which he was subjected to a double curse by God: The ground would no longer yield to him which was his 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 would come upon him and kill him. Cain settled in the land of Nod, east of Eden. He established a city and named it after his son Enoch (Gen 4:1-17).
In the New Testament, Abel is called righteous (Matt 23:35) and is named by Jesus as a just and innocent man who suffers and is killed (Lk 11:51). Abel’s sacrifice is judged greater than Cain’s because of his faith and this faith speaks beyond the grave (Heb 11:4). Cain is seen as the opponent of Abel (Heb 11:4) as a symbol for an evil way of living (Jude 11) and as someone whose works were wicked (1 Jn 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?” (Gen 4:9).