Genesis 4

12 When thou tillest the earth, then it shall not continue to give its strength to thee: thou shalt be groaning and trembling on the earth. 13 And Cain said to the Lord God, My crime is too great for me to be forgiven. 14 If thou castest me out this day from the face of the earth, and I shall be hidden from thy presence, and I shall be groaning and trembling upon the earth, then it will be that anyone that finds me shall slay me. 15 And the Lord God said to him, Not so, anyone that slays Cain shall suffer sevenfold vengeance; and the Lord God set a mark upon Cain that no one that found him might slay him. 16 So Cain went forth from the presence of God and dwelt in the land of Nod over against Eden.