Leviticus 11:39-40

And if any beast, of which ye may eat, die; he that toucheth the carcase thereof shall be unclean until the even.

If any beast of which ye may eat die. Every edible animal was to be prepared for food by being slaughtered-so that the flesh might be entirely emptied of the blood. But should such an animal-even an ox or a sheep-from disease or wounds, die a natural death, its carcass was unclean, and contact with it would occasion defilement for a brief period.