Genesis 36:24

24.This was that Anah that found the mules. Mules are the adulterous offspring of the horse and the ass. Moses says that Anal was the author of this connection. (131) But I do not consider this as said in praise of his industry; for the Lord has not in vain distinguished the different kinds of animals from the beginning. But since the vanity of the flesh often solicits the children of this world, so that they apply their minds to superfluous matters, Moses marks this unnatural pursuit in Anah, who did not think it sufficient to have a great number of animals; but he must add to them a degenerate race produced by unnatural intercourse. Moreover, we learn hence, that there is more moderation among brute animals in following the law of nature, than in men, who invent vicious admixtures.