Chasidut su Deuteronomio 25:16

With this in mind, we can understand why the great and holy souls took such pains to refine their behavior,³⁴Good behavior, “middos tovos,” in Hebrew, meaning being calm and composed rather than angry, industrious rather than lazy, joyful rather than melancholy, and so forth. and were so adamant in their fight against even the slightest corruption of conduct. They based their view on the Talmud, which says that the punishment for bad behavior is more severe than the punishment for marrying forbidden relatives and the like.³⁵The “bad behavior” discussed by the Gemara is that of cheating by using false measurements in a sales transaction (See Devarim, 25:16). However, the Hebrew term for conduct or behavior, “middot,” is the same as the word for measurement. In this way the author can justifiably take the term out of its context in the Gemara and apply it to all “middos ra’os (improper conduct),” anger, pride, and the like. This is clear in light of what we have explained above, that the soul is revealed through the stimulation of his behavior. If a man accustoms himself from his childhood to get excited about vain and worldly pleasures, then the portion of his soul that is revealed in this excitement is thereby blemished. In his behavior, he forces his soul to be associated with foolishness to the point where his soul will naturally wake up to spurious stimulation. He will then find it quite natural to invest his soul in the lowest of pursuits. This is akin to the two angels that fell and were blemished in the world.³⁶This is explained in the Chovot Hatalmidim (A Student’s Obligation), chapter 10.