Remember what Amalek did to you, on the way, when you were leaving Egypt…
Said Rabbi Yosef Yitchak of Lubavitch:
The numerical value (gematria) of the Hebrew word amalek is 240, the same as that of the word safek, “doubt.”
All things holy are certain and absolute. Torah is absolute, the mitzvot are absolute, divine providence is absolute. Amalek is doubt. Baseless, irrational doubt that cools the fervor of holiness with nothing more than a cynical shrug.