'Duty' in the Bible

“You shall not see your countryman’s ox or his sheep straying away or being stolen, and ignore [your duty to help] them; you shall certainly take them back to him.

You shall do this with his donkey or with his garment or with anything that your countryman has lost and you have found. You are not allowed to ignore [your duty to help] them.

You shall not see your countryman’s donkey or his ox fall down along the road, and ignore [your duty to help] them; you shall certainly help him lift it up.

“If brothers are living together and one of them dies without a son, the widow of the deceased shall not be married outside the family to a stranger. Her husband’s brother shall be intimate with her after taking her as his wife and perform the duty of a husband’s brother to her.

But if the man does not want to marry his brother’s [widowed] wife, then she shall go up to the gate [of the city, where court is held] to the elders, and say, ‘My brother-in-law refuses to continue his brother’s name in Israel; he is not willing to perform the duty of a husband’s brother.’