When the children of Israel were in the wilderness after they left Egypt, the Lord commanded Moses to "take unto thee Aaron thy brother, and his sons with him . . . to consecrate him, that he may minister unto me in the priest's office." (Ex. 28:1, 3.)
In Church History and Modern Revelation, Elder Joseph Fielding Smith wrote of the bestowal of the priesthood upon Aaron and his sons:"At that time the males of the entire tribe of Levi were chosen to be the priests instead of the first-born of all the tribes, and Aaron and his sons were given the presidency over the Priesthood thus conferred.
"Since that time it has been known as the Priesthood of Aaron; including the Levitical Priesthood. The males of the tribe of Levi from one month upwards at the time they were called, numbered 22,000 souls, and they were to be invested with authority from that time forth in Israel."
Elder Smith pointed out it should be remembered that the Melchizedek Priesthood was withdrawn from the people when Moses was taken away, so that the Aaronic Priesthood remained with the carnal law, or the law of Moses, until the coming of Jesus Christ.
"In the calling of Aaron and his sons, the Lord made it known that this presiding authority over this Priesthood should be handed down from father to son," Elder Smith explained. "This was true also of the Levitical, which is a division of the Aaronic. All who were of the tribe of Levi were entitled to be priests and to officiate in some capacity in this authority."
In Mormon Doctrine, Elder Bruce R. McConkie wrote: "Aaron's call to the Levitical ministry stands as the perfect example of the choosing of legal administrators to do the Lord's work; ever since that day, the legality of priestly administration has been determined by whether the professing minister was `called of God, as was Aaron', that is, by revelation and ordination, and with the full approval of the body of the Lord's true worshipers."
