Deuteronomy, Chapter 25, Verse 17-18
17 Bear in mind what Amalek did to you on the journey after you left Egypt, 18 how he surprised you along the way, weak and weary as you were, and struck down at the rear all those who lagged behind; he did not fear God.
How shall we deal with truly evil people?
In Judaism, the Amalekites came to represent the archetypal enemy of the Jews. In the Jewish folklore the Amalekites are considered to be the symbol of evil. This concept has been used by some Hassidic rabbis (particularly the Baal Shem Tov) to represent atheism or the rejection of God. Elliot Horowitz and Josef Stern suggest that Amalekites have come to represent an "eternally irreconcilable enemy" that wants to murder Jews, and that Jews in post-biblical times sometimes associate contemporary enemies with Haman or Amalekites, and that some Jews believe that pre-emptive violence is acceptable against such enemies.