Torah 249 · תורה רמ״ט

Strength is for the most part in the heart. When someone’s heart is mighty and he is not afraid of anyone or anything, he is able to perform awesome acts of strength and be victorious in battle because of his heart’s might and force—that he has no fear, and charges into the thick of the battle.

This is the aspect of “Who is strong? The one who conquers his evil inclination” (Avot 4:1). This is likewise the aspect of the strength of Shimshon, of whom it is said, “God’s spirit began to move him in the camp of Dan, between Tzorah and Eshtaol” (Judges 13:25). In those places God’s spirit came over him and he donned strength. That is, he received might and forceful strength in the heart, and through this performed awesome acts of strength.