Leviticus 20:25-26

You are therefore to make a distinction between the [ceremonially] clean animal and the unclean, and between the unclean bird and the clean; and you shall not make yourselves detestable by animal or by bird or by anything that crawls on the ground, which I have set apart from you as unclean. You are to be holy to Me; for I the LORD am holy, and have set you apart from the peoples (nations) to be Mine.