That’s Not Kosher!By Rabbi Jack Abramowitz
G-d then detailed to Moshe and Aharon the laws of kashrus (keeping kosher). (Rashi says that G-d spoke to Moshe, who spoke to Aharon.) It should be noted that the Torah doesn’t deal with the scientific categories of birds, mammals, fish, reptiles, etc. Rather, it organizes animals into such categories as beasts of the land, sea creatures, flying things and creeping things. So don’t be mistaken that the Torah thought the bat was a bird and a mouse was a reptile. A bat is a flying thing and a mouse is a creeping thing. The fact that they’re both mammals is immaterial.
In order to be kosher, a land animal must chew its cud and have fully-cloven hooves. An animal that has one sign or the other isn’t good enough. Sea creatures must have both fins and removable scales. Birds don’t have kosher signs. Rather, the Torah gives us a list of non-kosher birds. We infer certain things, such as we don’t eat birds of prey, but in practice we only eat birds that have a tradition of being kosher. (The big question is turkey, which is not indigenous to the Middle East and had no tradition. Basically, a turkey is just a big chicken under Jewish law.)
Certain insects are kosher. These are particular species of locusts that have four legs for walking and two for jumping. (While they may be identifiable, the practice of Ashkenazic Jews is not to eat them, as per the position of Rashi.)
If a person touched the carcass of a non-kosher animal, like a pig or a dog, he would become impure until the evening. Picking up the carcass would make his clothes impure as well, so not only he, but also his garments, would need to be immersed in a mikvah.
“Creeping things” whose corpses would render a person unclean include weasels, moles, lizards and other small animals. (There are eight in all, but we’re not 100% sure about all of their identities.) If a person touched one of these carcasses, he would be unclean until nightfall. If one of these dead creatures fell onto a vessel, a garment, or any other usable item, that object must be immersed in a mikvah and it would remain unclean until evening.