Deuteronomy 25:5-7

5“If brothers dwell together, and one of them dies and has no son, the widow of the dead man shall not be married to a stranger outside the family; her husband’s brother shall go in to her, take her as his wife, and perform the duty of a husband’s brother to her.

6And it shall be that the firstborn son which she bears will succeed to the name of his dead brother, that his name may not be blotted out of Israel.

7But if the man does not want to take his brother’s wife, then let his brother’s wife go up to the gate to the elders, and say, ‘My husband’s brother refuses to raise up a name to his brother in Israel; he will not perform the duty of my husband’s brother.’