Leviticus 11:3

Some have thought that in order to discountenance the most distant approach to idolatry, those creatures which the neighboring nations made their idols, were those which the LORD marked particularly as unclean; that they might be held in the greater abomination by the Israelites. Whether this be so or not, I do not say. But one observation I would make in this place concerning an error, which, for want of due attention, some Christians have fallen into, I mean respecting swine's flesh being so carefully abstained from by the Jews. It hath been thought that they eat it not, because CHRIST permitted the devil to enter into the herd of swine: Mark 5:13. Whereas a moment's consideration would convince, that as the Jews did not believe in our LORD himself, consequently they pay no attention to this miracle. This scripture of the Levitical law concerning the unclean beast, explains it. The hog cheweth not the cud, and therefore, though he be cloven-footed yet is he unclean.