Forces of Evil
The Torah tells us that Moshe Rabbeinu gathered the nation אחרי הכותו את סיחון, after he smote Sichon, the king of אמורי and Og, king of בשן. The Netivot Shalom said that these verses were necessary as a prerequisite to Moshe’s final address. They represented his ability to smash the negative forces in the world. These forces are sometimes referred to as the סיטרא אחרא, or the כח הקליפה, the force of the shell. There was then, and still exists today, two very powerful forces; those of good, and those of evil. When we do Mitzvot, we become attached to Good. When we sin, we distance ourselves and are in danger of being pulled to the negative side. The Sefer Hachinuch goes further when it goes into details about witchcraft. When speaking about sorcery and demons, the חינוך says that one of their main characteristics is that they are totally destructive. They tear down and do not rebuild. They disrupt the balance in the world between the higher and lower worlds. (Kind of sounds like Leftists, doesn’t it?) Moshe Rabbeinu realized all of this, and needed to be certain that these forces of evil were put to rest, so that he could elevate the nation, spiritually.