Then Judah said to Tamar his daughter-in-law, "Remain a widow in your father's house till my son Shelah is grown." For he said, "Lest he also die like his brothers." And Tamar went and dwelt in her father's house.

" If brothers dwell together, and one of them dies and has no son, the widow of the dead man shall not be [married] to a stranger outside [the family;] her husband's brother shall go in to her, take her as his wife, and perform the duty of a husband's brother to her.