Leviticus 11:26

The carcases of every beast which divideth the hoof, and is not clovenfooted, nor cheweth the cud, are unclean unto you: every one that toucheth them shall be unclean.

Cross-reference

Deuteronomy 14:8 specifies the pig as unclean because it has a split hoof but doesn't chew cud, echoing this verse's criteria.

Isaiah 52:11 uses the metaphor of touching unclean things to urge purity when leaving Babylon, referencing Levitical concepts.