Deuteronomy 25:5-10

⁵ If brothers dwell together, and one of them die, and have no son, the wife of the dead shall not be married outside to a stranger: her husband’s brother shall go in to her, and take her to him as wife, and perform the duty of a husband’s brother to her. ⁶ It shall be, that the firstborn whom she bears shall succeed in the name of his brother who is dead, that his name not be blotted out of Israel. ⁷ If the man doesn’t want 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 raise up to his brother a name in Israel; he will not perform the duty of a husband’s brother to me.” ⁸ Then the elders of his city shall call him, and speak to him: and if he stand, and say, “I don’t want to take her;” ⁹ then his brother’s wife shall come to 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 to the man who does not build up his brother’s house.” ¹⁰ His name shall be called in Israel, The house of him who has his shoe untied.