Numbers 20:24

Because ye rebelled This was one, but not the only reason. God would not have Moses and Aaron to carry the people into Canaan, for this reason also, to signify the insufficiency of the Mosaical law and Aaronical priesthood to make them perfectly happy, and the necessity of a better dispensation, and to keep the Israelites from resting in them, so as to be taken off from their expectation of the Messiah.