Mesillas Yesharim 165

In the birchos hashachar, we make the bracha of "ozer yisroel bi’gvurah". The term ozer refers to a belt that one girds himself with. Rav Kook explains that the belt distinguishes between the upper body and the lower body. The gevurah referred to is the ability to be able to categorize and distinguish between that which is good and that which is not, a primary step in zehirus.

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