Deuteronomy 25:5-9

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.’

8The elders of his city will summon him and speak with him. If he persists and says, ‘I don’t want to marry her,’

9then his sister-in-law will go up to him in the sight of the elders, remove his sandal from his foot, and spit in his face. Then she will declare, ‘This is what is done to a man who will not build up his brother’s house.’