Deuteronomy 25:5 in the World English Bible
If brothers dwell together, and one of them dies and has no son, the wife of the dead shall not be married outside to a stranger. Her husband’s brother shall go in to her, and take her as his wife, and perform the duty of a husband’s brother to her.
Context
4 Thou shalt not muzzle the ox when he treadeth out the corn.
5 If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not marry without unto a stranger: her husband’s brother shall go in unto her, and take her to him to wife, and perform the duty of an husband’s brother unto her.
6 And it shall be, that the firstborn which she beareth shall succeed in the name of his brother which is dead, that his name be not put out of Israel.