Deuteronomy 25:5

3Forty stripes he may give him, and not exceed: lest, if he should exceed, and beat him above these with many stripes, then thy brother should seem vile unto thee.

4Thou shalt not muzzle the ox when he treadeth out the corn.

5If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not marry 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 an husband’s brother unto her.

6And it shall be, that the firstborn which she beareth shall succeed in the name of his brother which is dead, that his name be not put out of Israel.

7And if the man like not to take his brother’s wife, then let his brother’s wife 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 my husband’s brother.