Deuteronomy 25:5-6

ISV(i) 5 Levirate Marriage“When two brothers are living together and one of them dies without leaving a son, his widow must not be married outside the family to a foreigner. Instead, the brother-in-law must go to her, take her as his wife, and by doing so perform the duty of a brother-in-law. 6 The firstborn whom she will bear will continue the name of the dead brother, so his name will not be erased from Israel.