Deuteronomy 25:5-7

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

6Now the firstborn that she bears is to carry on the name of his dead brother, so that his name will not be blotted out of Israel.

7But if the man does not want to take his brother’s widow, his brother’s widow is to go to the elders at the gate and say, ‘My brother-in-law refuses to carry on his brother’s name in Israel—he is unwilling to perform a brother-in-law’s duty for me.’