Deuteronomy 25:17-19

17Remember what Amalek did unto thee on the way, when ye came forth out of Egypt; 18how he met thee on the way, and smote the hindmost of thee, all the feeble that lagged behind thee, when thou wast faint and weary, and he feared not 1God. 19And it shall be, when Jehovah thy 2God shall have given thee rest from all thine enemies round about, in the land that Jehovah thy 3God giveth thee for an inheritance to possess it, that thou shalt blot out the remembrance of Amalek from under the heavens; thou shalt not forget it.