Deuteronomy 25:5-6

MSTC(i) 5 When brethren dwell together and one of them die and have no child, the wife of the dead shall not be given out unto a stranger: but her brother-in-law shall go in unto her and take her to wife and marry her. 6 And the eldest son which she beareth, shall stand up in the name of his brother which is dead, that his name be not put out in Israel.