Mules in Smiths Bible Dictionary

a hybrid animal, the offspring of a horse and an ass. "The mule is smaller than the horse, and is a remarkably hardy, patient, obstinate, sure-footed animal, living, ordinarily, twice as long as a horse." --McClintock and Strong's Cyclopedia. It was forbidden to the Israelites to breed mules, but sometimes they imported them. It would appear that only kings and great men rode on mules. We do not read of mules at all in the New Testament; perhaps therefore they had ceased to be imported.