'Duty' in the Bible

“When a man takes a bride, he must not go out with the army or be liable for any duty. He is free to stay at home for one year, so that he can bring joy to the wife he has married.

“When brothers live on the same property and one of them dies without a son, the wife of the dead man may not marry a stranger outside the family. Her brother-in-law is to take her as his wife, have sexual relations with her, and perform the duty of a brother-in-law for her.

But if the man doesn’t want to marry his sister-in-law, she must go to the elders at the city gate and say, ‘My brother-in-law refuses to preserve his brother’s name in Israel. He isn’t willing to perform the duty of a brother-in-law for me.’