Deuteronomy 25:7-9

7But if the man does not want to take his brother’s widow, his brother’s widow is to go to the elders at the gate and say, ‘My brother-in-law refuses to carry on his brother’s name in Israel—he is unwilling to perform a brother-in-law’s duty for me.’

8Then the elders of his town are to summon him and speak to him. And if he stands firm and says, ‘I do not desire to take her,’

9then his brother’s widow is to come to him in the sight of the elders, pull his sandal off his foot, spit in his face, and reply, ‘So will it be done to the man who does not build up his brother’s house.’