Genesis 6:19

Every living thing of all flesh] This comprehensive command is limited in the Primitive narrative (Genesis 7:2) to clean animals (such as sheep, oxen, and goats), and to beasts that are not clean (which by analogy means domestic animals, such as camels, asses, horses, etc.), and fowls. The inclusion of all living animals in the ark is the explanation which the tradition had to give, to account for a fact, otherwise inexplicable on its theory of a universal flood; namely, the presence in the world of so many different species of animals after such a destructive event.