"and you were faint and weary": Israel; "and did not fear the L-rd": Amalek.
(Ibid. 19) "And it shall be, when the L-rd your G-d gives you repose from all your enemies roundabout": so that they no longer band against you.
"in the land that the L-rd your G-d gives to you as an inheritance": In reward for this mitzvah, you will inherit the land.
"Wipe out the remembrance of Amalek from under the heavens": And thus is it written (Shemoth 17:14) "For I shall utterly blot out the remembrance of Amalek from under the heavens." That there be neither child nor grandchild (left of) Amalek under the heavens. And (Ibid. 16) "For a hand (in oath) upon the throne of the L-rd — The L-rd will war against Amalek from generation to generation!" The L-rd had sworn upon His throne of glory: He will leave over neither child or grandchild of Amalek, neither camel not ass — so that they not say: "This is a camel of Amalek." "Do not forget"" in your heart.