Commento su Levitico 11:23

'וכל שרץ העוף וגו‎ BUT ALL PROLIFIC CREATURES AMONG FOWL etc. — This repetition of the statement already made in verse 20 is intended to teach that if it has five feet it is clean (Sifra, Shemini, Chapter 5 10).

אשד לו ארבע דגלים, which have four legs. Torat Kohanim explains that the reason the Torah appears to repeat something here that has been written in verse 20 is to tell us that if such a creature has five legs it is permitted to be eaten. It would appear that the same holds true if such creatures have six or more legs. We need to examine why the Torah saw fit to write this legislation in an indirect way requiring us to arrive at the ruling that 5-legged winged swarming things are permitted by exegesis instead of writing outright that if such creatures have five legs we may eat them. Alternatively, the Torah could have written that any such creatures moving on more than 4 legs are permissible. Perhaps the Torah also had to inform us about the permissibility of brine in which forbidden locusts had been stored. Torat Kohanim had interpreted the repetition of the word שקץ הוא to be an exclusion, i.e. only the actual body of the winged swarming thing is prohibited. The Torah therefore had to write this verse in order to get this point across.

וכל שרץ העוף, “every flying teeming creature etc.,” Rashi explains the term שרץ העוף as applying to all small insect like creatures that move slowly on the ground, such as the common fly, etc. Nachmanides disagrees, as he cannot agree that any species of bird can be described as שרץ just because it is small in size. Neither is a bird called עוף just because it has a certain size. The עטלף is small and is listed as by the Torah as an עוף, whereas many species of locusts have legs which are larger than their bodies. If we accept Rashi’s definition of שרץ העוף, why is the עטלף not included as one of the שרץ העוף? Size of the body clearly is not the decisive factor in determining the difference between these two groups of flying creatures. The fact is that the Torah itself explains the nature of שרץ העוף in our verse, when it is described as walking on four legs, and as having jumping legs above its wings, these legs being employed as a launching pad to enable it to fly or jump. This is also why these creatures are not called עוף כנף, “winged bird,” or plain עוף, “bird.” Another feature of these שרץ העוף is that their neck and head instead of being above their bodies, are generally lower than the highest parts of the rest of their bodies.

It has five [feet], it is [ritually] clean. Otherwise, why does it say this when above it is written (v. 21-22): “However, these you may eat of all the flying insects that walk on four [legs]...” which implies that only these four species [mentioned] are permitted, but the rest of the flying insects that have four feet are prohibited to be eaten? Rather, it must be: “[This] comes and teaches [us]...” This raises a difficulty: Perhaps [we should instead learn] from this that if it has two legs it is pure? [The answer is:] It seems that a verse is surely not needed for one with two legs, for Scripture only says: “that walk on four [legs]” and not on two. A verse is needed, however, for five legs, because four legs are included in five. Therefore, it is needed to exclude that if it has five it is pure (Gur Aryeh).

וכל שרץ העוף, “and all winged swarming things;” in respect of fish and birds that are forbidden to eat, the Torah did not use the term טומאת מגע, ritual contamination through touching, it only wrote that we should detest them. The reason is that seeing that seeing that they have mostly been created in water, they are treated as if part of that domain. In accordance with this approach, we find that our sages in tractate keylim 17,13, state that any creatures that live in water are not subject to ritual contamination.