and animals with a divided hoof, because in such animals
the humors are well absorbed, and their nature well balanced: for
neither are they too moist, as is indicated by the hoof; nor are they
too earthy, which is shown by their having not a flat but a cloven
hoof. Of fishes they were allowed to partake of the drier kinds, of
which the fins and scales are an indication, because thereby the
moist nature of the fish is tempered. Of birds they were allowed to
eat the tamer kinds, such as hens, partridges, and the like. Another
reason was detestation of idolatry: because the Gentiles, and
especially the Egyptians, among whom they had grown up, offered up
these forbidden animals to their idols, or employed them for the
purpose of sorcery: whereas they did not eat those animals which the
Jews were allowed to eat, but worshipped them as gods, or abstained,
for some other motive, from eating them, as stated above (A. 3, ad
2). The third reason was to prevent excessive care about food:
wherefore they were allowed to eat those animals which could be
procured easily and promptly.

With regard to blood and fat, they were forbidden to partake of those
of any animals whatever without exception. Blood was forbidden, both
in order to avoid cruelty, that they might abhor the shedding of
human blood, as stated above (A. 3, ad 8); and in order to shun
idolatrous rites whereby it was customary for men to collect the
blood and to gather together around it for a banquet in honor of the
idols, to whom they held the blood to be most acceptable. Hence the
Lord commanded the blood to be poured out and to be covered with
earth (Lev. 17:13). For the same reason they were forbidden to eat
animals that had been suffocated or strangled: because the blood of
these animals would not be separated from the body: or because this
form of death is very painful to the victim; and the Lord wished to
withdraw them from cruelty even in regard to irrational animals, so
as to be less inclined to be cruel to other men, through being used
to be kind to beasts. They were forbidden to eat the fat: both
because idolaters ate it in honor of their gods; and because it used
to be burnt in honor of God; and, again, because blood and fat are
not nutritious, which is the cause assigned by Rabbi Moses (Doct.
Perplex. iii). The reason why they were forbidden to eat the sinews
is given in Gen. 32:32, where it is stated that "the children of
Israel . . . eat not the sinew . .