Answer:
   
   The prohibition comes from Torah, in the book Leviticus, Chapter 11,
   verses 2 through 8, in particular, verse 7:
    1. And the LORD spake unto Moses and to Aaron, saying unto them, 2
    2. Speak unto the children of Israel, saying, These are the beasts
       which ye shall eat among all the beasts that are on the earth.
    3. Whatsoever parteth the hoof, and is clovenfooted, and cheweth the
       cud, among the beasts, that shall ye eat.
    4. Nevertheless these shall ye not eat of them that chew the cud, or
       of them that divide the hoof: as the camel, because he cheweth the
       cud, but divideth not the hoof; he is unclean unto you.
    5. And the coney, because he cheweth the cud, but divideth not the
       hoof; he is unclean unto you.
    6. And the hare, because he cheweth the cud, but divideth not the
       hoof; he is unclean unto you.
    7. And the swine, though he divide the hoof, and be clovenfooted, yet
       he cheweth not the cud; he is unclean to you.
    8. Of their flesh shall ye not eat, and their carcase shall ye not
       touch; they are unclean to you.