Mules in Bible Times
Mules used by the Arabs of Bible lands. They scarcely ever breed the mule themselves, but instead import them from either the Lebanon district of Syria, or from Cyprus. The Arabs very seldom use the mule for the purposes of agriculture, but rather use it for riding or for carrying of burdens particularly in rocky country.27
Mules used in later Old Testament times. The mule is not mentioned in the Bible until the reign of King David.28
The law of Moses prohibited the rearing of any animals which were the result of the union of different species (Leviticus 19:19). So the Jews never bred mules, but evidently they thought the law did not prohibit them from using them. From the days of King David, they came to be used as beasts of burden, and for the saddle, and were imported from other countries, especially Egypt. Included in the tribute which King Solomon received from other nations was a quantity of "mules, a rate year by year" (I Kings 10:24, 25; II Chronicles 9:24).
[Manners And Customs of Bible Lands]