Sefer HaChinuch ספר החינוך

To not eat impure fowl: To not eat impure fowl, as it is stated (Leviticus 11:13), “And these you shall abominate from the fowl; they shall not be eaten, etc.”

That which we have written about the forbidden foods (Sefer HaChinukh 73, 147) is from the roots of the commandment.

From the laws of the commandment is that which they, may their memory be blessed, said (Chullin 59a), “The signs of the beast and animal are stated from the Torah” — meaning to say they are explicit in the Torah, and that is a hoof completely divided, like the ox and the sheep, and [that] it brings up the cud — “but the signs of the fowl were not stated,” since the Torah delineated for us by name all of the impure ones in the world. And since it is so, there is no need to write their signs — as any bird that is found in the world besides them is fit (kosher). And nonetheless since not every man is an expert in all of the species of which the Torah informed us, the Sages informed us of signs through which any man may recognize them and he will be able to eat of fowl, even though he may not recognize even one of the many impure species that are delineated in Scripture.

It comes out according to our words that anyone who knows well all those delineated in the Torah — which are twenty-four species — can eat from any other bird that he finds; as they said that any bird not mentioned in the tally of the impure ones in the Torah is fit. And [it is] like they, may their memory be blessed, said (Chullin 63b), “It is revealed and known in front of the One that spoke and the world came into being, that the pure birds are more than the impure ones — therefore He specified the impure ones,” meaning that He specified all of the impure ones in the world. That is the explanation according to most of the rabbis, that all of the impure ones in the world are mentioned in the Torah. And [for] the ones that do not recognize them, the Sages, may their memory be blessed, said (Chullin 59a) that these are their signs: It is known that any bird that tramples (is a predator) is from the impure ones in the Torah. And the understanding of a predator is meaning to say that he sinks his claws into another bird and injects poison into it, as is the custom of the hawk and other birds that people hunt with. And there are some that are not predators, but are also from the impure species.

And the Sages, may their memory be blessed, said to us as a general rule that anything that has in its body these three signs: That it has an extra digit — and that is the large digit that protrudes more than the other digits; a crop — that is a broad place at the end of the esophagus wherein the bird gathers the food at the beginning of the eating; and a gizzard that peels [away] — and that is a place in which the bird grinds the food, which is called ventrai in the vernacular, and it has a thin membrane inside the flesh, and that membrane peels off in some birds — once a bird has these three signs, it is known that it is not from an impure species, and it is permitted. These two general rules that we have generalized — one to forbid and one to permit all birds that have them — no man need ask an expert in birds about them. Rather he may forbid the forbidden and allow the permitted immediately, as there is no hesitation about this.

And it comes out according to this general principle that there are four signs of purity in fowl. And these are them: it is not a predator; an extra digit; a crop; and a gizzard that peels. And we have already generalized that any bird that is found to be lacking one of them, and that is the unique one among them — which is that it is not a predator, meaning that it is a predator — is always impure and one need not check any other sign. And it is not necessary to say if it is lacking all of them — that it does not have even one of these signs of purity — that it is forbidden. As behold, even the one — the unique one — forbids by itself, as we said; all the more so if all of them are lacking. And the eagle is also one that does not have any of the signs of purity. If a bird is found that is lacking two — meaning to say that it only has two signs of purity and is lacking the two others, and one of the two [signs] of purity found in it is that it is not a predator — any bird that is like this is pure to eat for anyone who recognizes the raven and any species of raven. As there is none among the impure like this except for the raven, since it does not trample but it has one sign in its body of the signs of purity. And that sign of purity is not fixed in each species of raven. Rather there is a type that has an extra digit and is not a predator; one that has a crop and is not a predator; and one that has a gizzard that peels and is not a predator. The general rule of the matter is that these two signs of purity are found in its species and not another species — so did some of the commentators explain. And there are some that said that the raven has two signs of purity in its body besides that it is not a predator.

If a bird is found that is lacking the three signs of purity and there is none remaining to it besides the unique one — and that is that it is not a predator — it is always pure. As there is none among the impure birds that do not have one of all the signs of purity in their bodies but is not a predator except for the ossifrage and the osprey, which are like this. And they are not found in settlements — and since they are not found in settlements, we are not in doubt about them. And there are some of the commentators that said that they were not found with our Rabbis, may their memory be blessed, but they are found now. And I [say] about them, “Do not be greatly righteous.” (Ecclesiastes 7:16)’ As [the Rabbis] said that they are not found in settlements — meaning to say, that they are always distant from inhabited places — and since their nature is like this, “the world stands forever” (Ecclesiastes 1:4), and the law is the same at all times. If three signs of purity are found in its body — and they are an extra digit, a crop and a gizzard that peels — it is known that it is fit, and [that also] the fourth is [in it] (like this); meaning to say that it is not a predator. As there is no bird in the world with these three signs that is a predator. And [so] he does not need to check about it at all, but rather he may eat it immediately. But if three signs of purity are found in it and one of the three is that it is not a predator, one must certainly be in doubt about it; as most of the impure ones are like this, that they have three signs like these. And every man must ask about such a bird if he does not recognize all of (the impure) the enumerated ones in the Torah. It comes out, according to our words, that any bird that is in doubt for us whether it is impure or pure will be in one of two ways: that it have three signs of purity, and one of them is that it is not a predator, as we said, that it should be in doubt [of being] among the many species of the impure; or that it have two signs of impurity and one of them is that it is not a predator, that it should be in doubt of being a raven and its species. But all of the other ways do not bring a doubt, but rather we judge it as pure or impure immediately. Place your mind to the thing, as it is so, according to this general rule of ours. And we have written this general rule according to some of the commentators, as there are many explanations given in these matters of birds. And our Rabbis, may their memory be blessed, said (Chullin 64b) that all birds that are in doubt are eaten according to tradition — meaning to say that if the people of a place received [a tradition] and were accustomed to eat it [with no question] under the assumption that it is pure — that we should have no hesitation about it at all, and there is no need to check it. And the rest of its details are in the third chapter of Chullin. (See Tur, Yoreh Deah 82.)

And [it] is practiced in every place and at all times by males and females. And one who transgresses it and eats a kazayit of impure fowl volitionally is lashed; and inadvertently, is exempted.