Leviticus 11:9

9These shall ye eat of all that are in the waters. Here, also, some who know little of religion, plausibly contend that God is acting the physician’s part, and distinguishing wholesome from unwholesome food. But although their opinion is sufficiently refuted by medical men themselves, yet, even if I should admit what they desire, they reason badly. For the purpose of God was other than to provide for the people’s health; and, because He had to do with a rude people, He chose common marks, being admonished by which they might gradually ascend to higher things. It would be useless to follow the allegories which Isychius has invented (44) and I would willingly bury in oblivion these triflings, except that many have such a leaning to subtleties, that sober views would scarcely please them, until the folly of these allegories shall have been convicted. I will say nothing of the scales and fins. If at first sight any should approve of what he says as to the names of the fish being omitted, because the Church seeks not. a name upon earth, and that the Church is signified by the fish, — let them consider whether it is consistent that the Church should only exist in the water; and, again, that the birds, which are nearer heaven, should be excluded from this honor; thirdly, that the clean animals should be rejected, as if they did not belong to the Church; lastly, that those who by their contagion pollute the Church should be counted amongst the elect, whose names are written in heaven; for certainly many of the fish are unclean. Those who will not acquiesce in these perspicuous reasons, I will allow to wander in their labyrinth. This simple view will satisfy the moderate and teachable, that the fish are not named, because the greater part of them were unknown to the Jews, whose country did not produce many of the river-fish, since it scarcely had any river besides the Jordan, whilst the sea-fish only visited the neighboring shores.