Charles Ellicott Commentary Leviticus 11:2

"Speak unto the children of Israel, saying, These are the living things which ye may eat among all the beasts that are on the earth." — Leviticus 11:2 (ASV)

These are the beasts which you shall eat among all ... — Better, These are the animals which you may eat of all ... . The dietary laws, which stand first in the general precepts about clean and unclean things, begin with the quadrupeds, or land animals, both domesticated and wild.

This is in accordance with the Hebrew division of the animal kingdom into four principal classes:

1. The land animals
2. The water animals
3. The birds of the air
4. The swarming animals

Although not specified here by name, the parallel regulations in Deuteronomy 14:4-5 enumerate the following ten animals: the ox, the sheep, the goat, the hart, the roebuck, the fallow deer, the wild goat, the pygang, the wild ox, and the chamois, with their various kindred species, which are not mentioned.

From the expression, “These are the animals,” the opinion arose during the Second Temple period that God actually caused specimens of every animal to pass before Moses and Aaron, in order to show them the actual creatures which are clean and unclean, just as the Lord caused every species to come to Noah into the ark.