At the end of this week's Torah portion, there is a section where the Torah commands us to remember what the people of Amalek did to the Jewish people when they left Egypt. In fact, some halakhic opinions state that the way to fulfill this biblical commandment to remember is to read this very section aloud.
In short, the story of Amalek is that, after the great miracles God performed for the Jewish people during their exodus from Egypt, no other nation on earth dared to fight against them. However, the people of Amalek did. In response to this arrogance and disrespect, God decreed that Amalek's actions would be remembered forever.
Now, the Amalekite people have not existed for many years; King David (more than 2,500 years ago) completely eliminated them. Given this, why is it necessary to remember them?
As with all matters in the Torah, there is a material manifestation of Amalek and a spiritual one. The physical Amalek no longer exists, but the spiritual one does. And regarding this, the Torah tells us to a) remember it and b) blot it out.
The spiritual Amalek resides within each of us and is essentially the coldness and indifference with which we face God. Amalek is the source of this indifferent attitude toward all that is holy and Divine.
And how do we fight indifference? By taking action. The Sefer HaChinuch, by Rabbi Aharon HaLevi of 13th-century Spain, explains that a person's heart is influenced by their actions. Even if a person doesn't truly feel what they are doing, isn't fully engaged and emotionally involved, but rather acts out of convenience or duty, etc., even so, through the repetition of good deeds, the heart is molded to fully feel what one is doing—that is, to erase coldness. Because a person is cold when they neither understand nor feel. And even if they do understand, given that the nature of the intellect is to be cold and calculating, it may be that even if they rationally agree with something, they don't feel it.
And perhaps that is why the last verse of this week's section says that one must blot out Amalek from "under heaven," that is, one must begin with what is below heaven, on earth, with practical action, with good habits, and in that way one can modify what is "in heaven," so to speak, reveal the essence of one's soul.