Deuteronomy 25:5-6

Evangelical Heritage Version

⁵ When brothers live together and one of them dies without having children, the wife of the deceased brother is not to marry a stranger from outside the family. Her brother-in-law is to come and take her as his wife and perform for her the duty of a brother-in-law. ⁶ The firstborn that she bears will be recognized as a son who carries on the name of his deceased brother, so his name will not be erased from Israel.