Musar su Levitico 11:47

The forbidden foods are worse in this regard than all other sins since they literally enter a person's body and become flesh of his flesh. And in order to teach us that it is not only the unkosher animals and creatures that contain this Tuma (spiritual contamination) but rather even the disqualified Kosher animals themselves (Treifot) also. Scripture says: "to distinguish between the impure (Tamei) and the pure (Tahor)" (Vayikra 11:47), and the explanation received by our Rabbis of blessed memory:

At the conclusion of this whole chapter the Torah writes: להבדיל בין הטמא ובן הטהור, "In order to make a distinction between what is impure and what is pure," etc. When we recite the benediction of הבדלה, at the conclusion of the Sabbath, the formula is: המבדיל בין קדש לכל, בין ישראל לעמים, "Who separates between the sacred and the profane, between the people of Israel and the other nations." This means that there is a vital difference between (even) ordinary Israelites, non-priests, and members of the Gentile nations.