be of the family of Aaron, a descendant of his; it was not enough that he was of the tribe of Levi, but he must descend from Aaron, either in the line of Eleazar or of Ithamar: shall put them on seven days; the next successor was to wear the garments seven days running: when he cometh into the tabernacle of the congregation to minister in the holy place; to offer sacrifice in the court of the tabernacle, on the altar of burnt offering, and to offer incense on the altar of incense, and to trim the lamps of the candlestick, and to put the shewbread on the table.