Deuteronomy 25:5-10

If brethren dwell together, and one of them die, and have no son, the wife of the dead shall not be married without unto a stranger: her husband’s brother shall go in unto her, and take her to him to wife, and perform the duty of a husband’s brother unto her. And it shall be, that the first-born that she beareth shall succeed in the name of his brother that is dead, that his name be not blotted out of Israel. And if the man like not to take his brother’s wife, then 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 the duty of a husband’s brother unto me. Then the elders of his city shall call him, and speak unto him: and if he stand, and say, I like not to take her; then shall his brother’s wife come unto him in the presence of the elders, and loose his shoe from off his foot, and spit in his face; and she shall answer and say, So shall it be done unto the man that doth not build up his brother’s house. And his name shall be called in Israel, The house of him that hath his shoe loosed.