Supererogation in the Bible

Ezekiel 33:12-13 Therefore, thou son of man, say unto the children of thy people, The righteousness of the righteous shall not deliver him in the day of his transgression: as for the wickedness of the wicked, he shall not fall thereby in the day that he turneth from his wickedness; neither shall the righteous be able to live for his righteousness in the day that he sinneth. 13 When I shall say to the righteous, that he shall surely live; if he trust to his own righteousness, and commit iniquity, all his righteousnesses shall not be remembered; but for his iniquity that he hath committed, he shall die for it.
Luke 17:10 So likewise ye, when ye shall have done all those things which are commanded you, say, We are unprofitable servants: we have done that which was our duty to do.