Summa Theologica I-II, q. 102: Of the Causes of the Ceremonial Precepts
The hawk, which helps men to seize the prey, is a figure of those who assist the strong to prey on the poor. The screech-owl, which seeks its food by night but hides by day, signifies the lustful man who seeks to lie hidden in his deeds of darkness. The cormorant, so constituted that it can stay a long time under water, denotes the glutton who plunges into the waters of pleasure. The ibis is an African bird with a long beak, and feeds on snakes; and perhaps it is the same as the stork: it signifies the envious man, who refreshes himself with the ills of others, as with snakes. The swan is bright in color, and by the aid of its long neck extracts its food from deep places on land or water: it may denote those who seek earthly profit through an external brightness of virtue. The bittern is a bird of the East: it has a long beak, and its jaws are furnished with follicules, wherein it stores its food at first, after a time proceeding to digest it: it is a figure of the miser, who is excessively careful in hoarding up the necessaries of life. The coot [*Douay: 'porphyrion.' St. Thomas' description tallies with the coot or moorhen: though of course he is mistaken about the feet differing from one another.] has this peculiarity apart from other birds, that it has a webbed foot for swimming, and a cloven foot for walking: for it swims like a duck in the water, and walks like a partridge on land: it drinks only when it bites, since it dips all its food in water: it is a figure of a man who will not take advice, and does nothing but what is soaked in the water of his own will. The heron [*Vulg.: 'herodionem'], commonly called a falcon, signifies those whose "feet are swift to shed blood" (Ps. 13:3). The plover [*Here, again, the Douay translators transcribed from the Vulgate: 'charadrion'; 'charadrius' is the generic name for all plovers.], which is a garrulous bird, signifies the gossip. The hoopoe, which builds its nest on dung, feeds on foetid ordure, and whose song is like a groan, denotes worldly grief which works death in those who are unclean. The bat, which flies near the ground, signifies those who being gifted with worldly knowledge, seek none but earthly things. Of fowls and quadrupeds those alone were permitted which have the hind-legs longer than the forelegs, so that they can leap: whereas those were forbidden which cling rather to the earth: because those who abuse the doctrine of the four Evangelists, so that they are not lifted up thereby, are reputed unclean. By the prohibition of blood, fat and nerves, we are to understand the forbidding of cruelty, lust, and bravery in committing sin.
Reply to Objection 2Men were wont to eat plants and other products of the soil even before the deluge: but the eating of flesh seems to have been introduced after the deluge; for it is written (Gn. 9:3): "Even as the green herbs have I delivered. . . all" flesh "to you." The reason for this was that the eating of the products of the soil savors rather of a simple life; whereas the eating of flesh savors of delicate and over-careful living. For the soil gives birth to the herb of its own accord; and such like products of the earth may be had in great quantities with very little effort: whereas no small trouble is necessary either to rear or to catch an animal. Consequently God being wishful to bring His people back to a more simple way of living, forbade them to eat many kinds of animals, but not those things that are produced by the soil. Another reason may be that animals were offered to idols, while the products of the soil were not.
The Reply to the Third Objection is clear from what has been said (ad 1).
Reply to Objection 4Although the kid that is slain has no perception of the manner in which its flesh is cooked, yet it would seem to savor of heartlessness if the dam's milk, which was intended for the nourishment of her offspring, were served up on the same dish. It might also be said that the Gentiles in celebrating the feasts of their idols prepared the flesh of kids in this manner, for the purpose of sacrifice or banquet: hence (Ex. 23) after the solemnities to be celebrated under the Law had been foretold, it is added: "Thou shalt not boil a kid in the milk of its dam." The figurative reason for this prohibition is this: the kid, signifying Christ, on account of "the likeness of sinful flesh" (Rom. 8:3), was not to be seethed, i.e. slain, by the Jews, "in the milk of its dam," i.e. during His infancy. Or else it signifies that the kid, i.e. the sinner, should not be boiled in the milk of its dam, i.e. should not be cajoled by flattery.
Reply to Objection 5The Gentiles offered their gods the first-fruits, which they held to bring them good luck: or they burnt them for the purpose of secrecy. Consequently (the Israelites) were commanded to look upon the fruits of the first three years as unclean: for in that country nearly all the trees bear fruit in three years' time; those trees, to wit, that are cultivated either from seed, or from a graft, or from a cutting: but it seldom happens that the fruit-stones or seeds encased in a pod are sown: since it would take a longer time for these to bear fruit: and the Law considered what happened most frequently. The fruits, however, of the fourth year, as being the firstlings of clean fruits, were offered to God: and from the fifth year onward they were eaten.
The figurative reason was that this foreshadowed the fact that after the three states of the Law (the first lasting from Abraham to David, the second, until they were carried away to Babylon, the third until the time of Christ), the Fruit of the Law, i.e. Christ, was to be offered to God. Or again, that we must mistrust our first efforts, on account of their imperfection.
Reply to Objection 6It is said of a man in Ecclus. 19:27, that "the attire of the body. . . " shows "what he is." Hence the Lord wished His people to be distinguished from other nations, not only by the sign of the circumcision, which was in the flesh, but also by a certain difference of attire. Wherefore they were forbidden to wear garments woven of woolen and linen together, and for a woman to be clothed with man's apparel, or vice versa, for two reasons. First, to avoid idolatrous worship. Because the Gentiles, in their religious rites, used garments of this sort, made of various materials. Moreover in the worship of Mars, women put on men's armor; while, conversely, in the worship of Venus men donned women's attire. The second reason was to preserve them from lust: because the employment of various materials in the making of garments signified inordinate union of sexes, while the use of male attire by a woman, or vice versa, has an incentive to evil desires, and offers an occasion of lust. The figurative reason is that the prohibition of wearing a garment woven of woolen and linen signified that it was forbidden to unite the simplicity of innocence, denoted by wool, with the duplicity of malice, betokened by linen. It also signifies that woman is forbidden to presume to teach, or perform other duties of men: or that man should not adopt the effeminate manners of a woman.
Reply to Objection 7As Jerome says on Mat. 23:6, "the Lord commanded them to make violet-colored fringes in the four corners of their garments, so that the Israelites might be distinguished from other nations." Hence, in this way, they professed to be Jews: and consequently the very sight of this sign reminded them of their law.
When we read: "Thou shalt bind them on thy hand, and they shall be ever before thy eyes [Vulg.: 'they shall be and shall move between thy eyes'], the Pharisees gave a false interpretation to these words, and wrote the decalogue of Moses on a parchment, and tied it on their foreheads like a wreath, so that it moved in front of their eyes": whereas the intention of the Lord in giving this commandment was that they should be bound in their hands, i.e. in their works; and that they should be before their eyes, i.e. in their thoughts. The violet-colored fillets which were inserted in their cloaks signify the godly intention which should accompany our every deed. It may, however, be said that, because they were a carnal-minded and stiff-necked people, it was necessary for them to be stirred by these sensible things to the observance of the Law.
Reply to Objection 8Affection in man is twofold: it may be an affection of reason, or it may be an affection of passion. If a man's affection be one of reason, it matters not how man behaves to animals, because God has subjected all things to man's power, according to Ps. 8:8: "Thou hast subjected all things under his feet": and it is in this sense that the Apostle says that "God has no care for oxen"; because God does not ask of man what he does with oxen or other animals.