The 188th mitzvah is that we are commanded to wipe out — from among all the descendants of Esav — the descendants of Amalek, male and female, young and old.

The source of this commandment is G‑d's statement1 (exalted be He), "Wipe out the memory of Amalek."

We have mentioned previously2 the statement of our Sages,3 "The Jewish people were commanded three mitzvos upon entering the Land of Israel: to appoint a king, to build the Beis HaMikdash, and to destroy the descendants of Amalek."

Waging war against Amalek is also a milchemes mitzvah [obligatory war].4

The details of this mitzvah are explained in the eighth chapter of tractate Sotah.