Leviticus 11:44

Ye shall be holy; by which he gives them to understand, that all these cautions and prohibitions about the eating or touching of these creatures was not for any real uncleanness in them, all being God's good creatures, but only that by the diligent observation of these rules they might learn with greater care to avoid all moral pollutions, and to keep themselves from all filthiness of flesh and spirit, and particularly from all familiar and intimate converse with notorious sinners.