Therefore it shall be, when the LORD thy God hath given thee rest from all thine enemies round about, in the land which the LORD thy God giveth thee for an inheritance to possess it, that thou shalt blot out the remembrance of Amalek from under heaven; thou shalt not forget it.

When the LORD your God gives you rest from the enemies around you in the land that He is giving you to possess as an inheritance, you are to blot out the memory of Amalek from under heaven. Do not forget!