Numbers 8:20

20.And Moses, and Aaron, and all the congregation The Levites also are now inaugurated for the performance of their duties, but in their proper order, because their condition was inferior. Here it must be noted that the sons of Moses and their descendants were placed in this lower rank, and excluded from all expectation of the priesthood. Hence the ingratitude of the whole people, and especially of the tribe of Levi, was all the more base, when they presumptuously sought the honor from which Moses had shut out his children for ever. It was then no ordinary act of obedience in him to execute what God had appointed respecting the Levites. Aaron is here mentioned, because he consecrated the Levites in right of his priesthood. As regards the people, their consent is merely commended, because they agreed to what was the pleasure of God. But this virtue in them only increased their ignominy afterwards, when they sought to overthrow that divine decree of which they had approved.