Deuteronomy 25:5-9

5If brethren dwell together, and one of them die, and have no son, the wife of the dead shall not marry a stranger abroad: her husband's brother shall go in unto her, and take her to him as wife, and perform the duty of a husband's brother unto her.

6And it shall be, that the firstborn that she beareth shall stand in the name of his brother who is dead, that his name be not blotted out from Israel.

7But if the man like not to take his brother's wife, his brother's wife shall go up to the gate unto the elders, and say, My husband's brother refuseth to raise up unto his brother a name in Israel: he will not perform for me the duty of a husband's brother.

8Then the elders of his city shall call him and speak unto him; and if he stand to it and say, I like not to take her;

9then shall his brother's wife come near to him before the eyes of the elders, and draw his sandal from his foot, and spit in his face, and shall answer and say, So shall it be done unto the man that will not build up his brother's house.