Leviticus 11:47

for making distinction between the unclean and the clean; between the animal whose flesh may be eaten, and the animal whose flesh may not be eaten.

To differentiate among birds and creatures of the water

that are eaten i.e., that are permissible for food ...

that will not be eaten according to the Torah.

TO MAKE A DISTINCTION BETWEEN THE UNCLEAN AND THE CLEAN. This means that we should distinguish between all things mentioned above, between the unclean and the clean, with regard to impurity[through contact]. AND BETWEEN THE ANIMAL THAT MAY BE EATEN. This is connected with the word “soul” mentioned [in the preceding verse], thus meaning: “and between the living animal that may be eaten.” Scripture is thus stating that we should distinguish as far as eating is concerned, between the living animal that may be eaten according to the Torah in the waters and upon the earth, and the animal in them that may not be eaten. In the Torath Kohanim the Rabbis said:. “And ‘hachayah’ (the beast) that may not be eaten. The Sages say, this establishes a prohibition against eating a [forbidden type of] beast.” (beast) is included in the term beheimah (cattle), as explained above in Verse 24, yet Scripture mentioned here a specific prohibition with regard to a forbidden chayah. If so, there is a special negative commandment regarding it.
Now Rashi wrote: “To make a distinction between the unclean and the clean. Is it necessary to tell us to distinguish between the cow and the ass? Have they not clearly been defined already [by distinguishing signs]? But the meaning is: [to make a distinction between] that which is forbidden for you and that which is permitted for you, between the case of an animal of which only half of the windpipe was cut, [in which case, even if he cut through the whole gullet, it may not be eaten], and the case of an animal of which the greater part of the windpipe [or the entire windpipe] was cut through, [in addition to the gullet, or the greater part of it being cut through, which is permitted to be eaten].” There [in Tractate Chullin] it is taught: “And how much is there between half and the greater part of it? As much as a hair’s breadth,” [and it is this which requires ‘making a distinction’]. Do not be disturbed here because of that which they said there in the Gemara that it must be “a greater part which is apparent to the eyes” [thus a mere hair’s breadth would not be sufficient], for the meaning of that was only in order to exclude the opinion of the Sage who says that half and half is treated as if the majority [was cut through]; therefore they said that the part cut through must actually be a greater part, which is apparent to the eyes, not a half which we only treat in our minds [as the greater part], and we say that “the greater part” was cut through since the part not cut through is not larger than it [the part which was cut through]. But so long as more than half was [actually] cut through, it may be eaten, even if it be only by as much as a hair’s breadth, as is clearly explained in that Beraitha, and as it emerges from the discussion of the Gemara.
Tazria