The Ultimate Moses and Aaron
Moses (see Palace Prince To Sinai Shepherd) and Aaron (see Aaron: The Prophet's Prophet) are two of the most famous people, both Levites (as was John the Baptist - see The Prophet Of The Judean Wilderness), of Bible History. They were however much more. Both served as minor portrayals of Jesus Christ, one as a "deliverer" of God's people, the other as a "high priest" through whom atonement for the people's sins was made (just as, moreover, King David also filled a prophetic role of the coming Messiah i.e. Christ was descended from Judah, as was His physical ancestor David, not from Levi, as were Moses and Aaron; see Israelite Monarchy - The Messiah). All of those offices (and far, far more - see Christ The Creator) were held by Christ before Moses, Aaron or David were ever born:
"7:9 And as I may so say, Levi also, who receiveth tithes, payed tithes in Abraham [see Abraham's Journey, The Exodus Prophecy and Circumcision]. 7:10 For he was yet in the loins of his father, when Melchisedec met him [see Melchizedek: A Portrayal Of Christ and 'Before Abraham Was, I AM']. 7:11 If therefore perfection were by the Levitical priesthood, for under it the people received the law, what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron? 7:12 For the priesthood being changed, there is made of necessity a change also of the law. 7:13 For he of whom these things are spoken pertaineth to another tribe, of which no man gave attendance at the altar.
"For they drank of that spiritual Rock that followed them: and that Rock was Christ"
Moses was the Deliverer's prophet (see The Master's Messenger), the leader of God's people as they were all being led by Christ.
"10:1 Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; 10:2 And were all baptized unto Moses in the cloud and in the sea [see Why Through The Sea?]; 10:3 And did all eat the same spiritual meat; 10:4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ. 10:5 But with many of them God was not well pleased: for they were overthrown in the wilderness.
No mere human can pay the atonement price for all of humanity. Aaron's priesthood was merely a portrayal of the Son of God who would come to do what no man could.
"9:11 But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building [see The Messiah's Triumphal Entry Into The Temple]; 9:12 Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us [see the Fact Finder question below and What Is Jesus Christ Doing Right Now?].
Fact Finder: Where was the "mercy seat"?