Deut 25.5If 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.
Mat 22.24Saying, Master, Moses said, If a man die, having no children, his brother shall marry his wife, and raise up seed unto his brother.