Luke 17:9

Doth he thank that servant because he did the things that were commanded him? I trow not.

No special gratitude is owed to a servant simply for carrying out what he was ordered to do. Even when believers have done all things that were commanded them, they are still to reckon themselves unprofitable servants who have done no more than their duty.

Doing one's duty in this way is the ground of humble service, not a cause for proud boasting. It forbids overvaluing one's own work while demeriting others and looking upon the work of fellow laborers as inferior.