Mules in the Old Testament
The first Scriptural reference to the mule is in connection with the sheep-shearing feast planned by Absalom for the plot against Amnon. It says: "All the king's sons arose, and every man got him up upon his mule, and fled" (II Samuel 13:29). Each prince had a mule for his personal travel use, and thus this animal had taken the place of the donkey for such use. The mule was used by King David when he traveled in state, and to ride upon the mule belonging to the king was considered to be much the same thing as sitting upon the throne of the king. Thus David said concerning Solomon whom he wanted to make king to succeed him: "Take with you the servants of your lord, and cause Solomon my son to ride upon mine own mule, and bring him down to Gihon" (I Kings 1:33).
Adonijah, who attempted to usurp the throne against the wishes of his father, heard that Solomon had ridden on the mule of David, he knew thereby that he had been made the new king (I Kings 1:44f).
By the time of Isaiah, the mule was in common use. The prophet says: "And they shall bring all your brethren for an offering unto the Lord out of all nations upon horses, and in chariots, and in litters, and upon mules, and upon swift beasts, to my holy mountain Jerusalem" (Isaiah 66:20). Kings had especially made use of them, as Ahab who was much concerned about keeping his mules alive in time of famine (I Kings 18:5). The Bible does not anywhere mention the obstinate disposition of the mule. A reference by the Psalmist says: "Be ye not as the horse, or as the mule, which have no understanding: whose mouth must be held in with bit and bridle, lest they come near unto thee" (Psalm 32:9). But this is not a reference to that trait of character for which the mule is noted today in the West. [Manners And Customs of Bible Lands]