'Obligation' in the Bible

He said, ‘A hundred measures of [olive] oil.’ And he said to him, ‘Take your bill, and sit down quickly and write fifty.’

Then he said to another, ‘And how much do you owe?’ He said, ‘A hundred measures of wheat.’ He said to him, ‘Take your bill, and write eighty.’

So you too, when you have done everything that was assigned and commanded you, say, ‘We are unworthy servants [undeserving of praise or a reward, for we have not gone beyond our obligation]; we have merely done what we ought to do.’”