'Duty' in the Bible

Now while Zechariah was serving as priest before God when his division was on duty,

So you too, when you have done everything you were commanded to do, should say, 'We are slaves undeserving of special praise; we have only done what was our duty.'"

But if a widow has children or grandchildren, they should first learn to fulfill their duty toward their own household and so repay their parents what is owed them. For this is what pleases God.

Give a shepherd's care to God's flock among you, exercising oversight not merely as a duty but willingly under God's direction, not for shameful profit but eagerly.