הלכה על מגילה 35:13

From the laws of the commandment is that which our Rabbis, may their memory be blessed, said (Megillah 18a) that the obligation of this remembrance is with the heart and with the mouth (see Sefer HaChinukh 330). As so is it in Sifrei, Parshat Bechukotai (at the beginning), "'Remember what Amalek did' - could it be with the heart? When it says 'do not forget' - behold, [this refers to] the forgetting of the heart. Behold, what is [the purpose of] 'Remember?' That it should be recited in your mouth." To here is [what is written] in Sifrei. [It is] in order to not forget the thing, lest the enmity be weakened and be removed from the hearts over the length of time.