Musar к Шмот 22:30

והיו לי הלוים . Anyone whose roots are in a holy domain must also sanctify himself in an increased measure. This is why the tribe of Levi who was chosen specifically underwent an additional sanctification. G–d had previously said in Exodus 22,30, of all the Israelites "ואנשי קודש תהיו לי," "you shall be holy people to Me!" Afterwards G–d sanctified the Levites and added "the Levites will belong to Me." Since G–d had done this at that time, it behooves the Levites to apply stricter rules of sanctity to themselves also in our times.

He also diminishes his stature as a human being thereby [(by speaking lashon hara)] until he emerges "worse than a dog," as Chazal have said (Pesachim 118a): "One who speaks lashon hara … deserves to be thrown to the dogs, it being written (Shemoth 23:1): 'You shall not receive a false report,' which is read as you shall not spread, which is preceded by (Ibid. 22:30): '…to the dog shall you throw it.'" The rationale is obvious, as written by the Maharal of Prague: "For the dogs guarded themselves when necessary, from 'sharpening their tongues,' as it is written (Ibid. 11;7): 'And against all the children of Israel, a dog shall not sharpen its tongue' — and he [(a human being)], whom the L-rd accorded understanding and knowledge could not restrain his yetzer from this [(lashon hara)] — wherefore he is 'worse' than a dog."

And, likewise, one who is accustomed to eat unkosher meat or to feed it to a Jew. And this is intimated in the Torah, it being written (Shemoth 23:1): "And men of holiness shall you be to Me, and flesh torn in the field you shall not eat. To the dog shall you throw it," after which it is written (Ibid. 23:1): "You shall not spread a false report." It emerges, then, that the verse of "To the dog shall you throw it" is found between these two sins — eating treifah [torn flesh] and speaking lashon hara, to teach us that for these two sins, a man may be reincarnated as a dog. And this is what King David, may peace be upon him, intimated in (Psalms 22:21): "Rescue from the sword, my soul; [rescue] from the dog, my soul," followed by "I will speak Your name to my brothers, etc." That is, I do not use my tongue to speak lashon hara, to be punished therefor by this dreadful reincarnation, but I use it to praise You and to exhort Israel, that they should fear You and praise You. And know that the Kabbalists have said that even though when a man is reincarnated in the form of another man he is unaware of his prior state, still when he is reincarnated as an animal or as a bird, he is aware of his prior state and suffers terribly at having descended from heaven from the form of a man to the form of a beast. Therefore, every man should fear and tremble and be soft of heart while he yet lives, while he yet has free will and knows his G-d, so that He forgives his sins and removes His wrath from him. And when his soul leaves him he will rest in peace and repose in His shade in Gan Eden. For He is gracious and merciful and abundant in lovingkindness. And (Berachoth 34b): "In the place where penitents stand, absolute Tzaddikim cannot stand." Until here, the words of the Sefer Charedim, in short.