The ceremonies connected with the consecration of the Levites had much in common with the regulations for cleansing of lepers. Originally, the firstborn had been the servants of the sanctuary, but, owing to the worship of the Golden Calf, they lost this prerogative, and the Levites replaced them. It was for this reason that the Levites were obliged to observe regulations similar to those for the cleansing of lepers, because they took the place of men who by their sins had defiled themselves.
The offerings that the Levites brought on this occasion consisted of two bullocks, on for a burnt offering whenever the congregation, seduced by others, commits idolatry; and Israel would not have worshipped the Golden Calf had not the mixed multitude misled them. "But whosoever worships an idol, by this act renounces the whole Torah," hence did the Levites have to offer up another bullock for a sin offering, in accordance with the law that "if the whole congregation of Israel have done somewhat against any of the commandments of the Lord concerning things which should not be done, and are guilty, then they shall offer up a young bullock for the sin."
As the Levites had been chosen "to do the service of the children of Israel in the Tabernacle of the congregation, and to make an atonement for the children of Israel," God ordered all the congregation of Israel to be present at the consecration of the Levites, for whosoever had a sin offering up for himself must in person bring it to the Tabernacle. Therefore, too, did the elders of Israel have to put their hands upon the Levites, according to the prescription that the elders must put their hands upon the sin of the congregation.
Aaron, like the elders, participated in the ceremony of the consecration, lifting up every single Levite as a token that he was now dedicated to the sanctuary. Aaron's extraordinary strength is proven by the fact that he was able to lift up twenty-tow thousand men in one day.