Deuteronomy 25:7-9

7And if the man does not wish to take his brother's wife, then his brother's wife shall go up to the gate to the elders and say, 'My husband's brother refuses to perpetuate his brother's name in Israel; he will not perform the duty of a husband's brother to me.'

8Then the elders of his city shall call him and speak to him, and if he persists, saying, 'I do not wish to take her,'

9then his brother's wife shall go up to him in the presence of the elders and pull his sandal off his foot and spit in his face. And she shall answer and say, 'So shall it be done to the man who does not build up his brother's house.'