הלכה אויף דברים 28:19

It is a Positive Commandment to obliterate Amalek, as it says, “erase the memory of Amalek” (Deut. 28:19). It is a Positive Commandment to perpetually remember their wicked deeds and their ambush in order to arouse our enmity against them, as it says, “remember what Amalek did to you” (Deut. 25:17). By Tradition we have learned that “remember” means by speech, “do not forget” (Deut. 25:19) – in one’s heart; for it is forbidden to forget their enmity and hatred.