Deuteronomy 25:5-7

5“When brothers live on the same property and one of them dies without a son, the wife of the dead man may not marry a stranger outside the family. Her brother-in-law is to take her as his wife, have sexual relations with her, and perform the duty of a brother-in-law for her.

6The first son she bears will carry on the name of the dead brother, so his name will not be blotted out from Israel.

7But if the man doesn’t want to marry his sister-in-law, she is to go to the elders at the city gate and say, ‘My brother-in-law refuses to preserve his brother’s name in Israel. He isn’t willing to perform the duty of a brother-in-law for me.’