So to recap quickly. Adam was the first priest and he was supposed to offer the priestly sacrifice for his bride-himself and he didn’t. God promised there would be a Saviour who would. The priesthood got seriously messed up by Cain but was continued in the way it was meant to through father to son from Seth through to Noah and Melchizedek. So to Abraham until Moses where the Golden Calf Incident ended the priesthood of father and first born son. With the authority given him by God Moses took the priesthood and gave it only to the fathers and sons of the tribe of Levi and that is how it was as Israel entered the Promised Land.
The priesthood remained with the sons of Levi from then on with the remarkable exceptions of David and Solomon both of the tribe of Judah who received the priesthood of Melchizedek, that is the priesthood of father and first born son. Unfortunately Solomon became a very bad king and priest and as a result Israel was split and eventually vanished. The southern kingdom of Judah survived for a while and then it too was subsumed. The Levitical priesthood remained in diaspora and some priests returned to the Promised Land when the tribes of Judah and Benjamin returned.
Then at last the time came for the Messiah, Prophet, Priest and King.
At the beginning of the New Testament we find Zachariah of the tribe of Levi is High Priest and he is to enter the Holy of Holies in the Temple. This could only be done by the High Priest and then only once a year on the Feast of Yom Kippur-the Day of Atonement. The priest would come out of the Holy of Holies and offer the Blessing to the people for the forgiveness of their sins. Of course that day the Blessing didn’t take place because the Angel struck Zachariah dumb for his refusal to believe what God had said.
John the Baptist, son of Zachariah became the next priest in that line and it was he who baptised Jesus who came to him at the age of thirty. This is the age a man could be ordained in the tradition of the priesthood. However we remember that although Jesus obviously was well related to the tribe of Levi, he was himself of the tribe of Judah. His priesthood therefore is the priesthood of David and Solomon (of the tribe of Judah)-that is the old priesthood of Melchizedek. Jesus is a priest, a First Born Son.
When we celebrate Epiphany we remember the Magi brought Him gifts of gold, frankincense and myrrh. each gift symbolised that Christ was King, Priest and Prophet-just as David had been. Jesus was the new Adam and the new David. (He is also, of course The Son of God)
The Levitical priesthood at this point has gone the way of the priesthood of Fathers and First Born Sons at the Golden Calf Incident. “We have no king but Caesar!” (A pagan man-god) they cry. Then they offer their sacrifice like Cain did-they offer the innocent man. The High Priest who should have been bowing down to the Prophet, Priest and King before him, hands him over to be crucified instead. The Levitical priesthood was finished. Forty years later (a generation) the Temple and the priesthood are finished.
Jesus though carried out His role of High Priest perfectly. Where Adam forgot about the Tree of Life when it came to saving Eve, Jesus embraced the Cross to save His Bride the Church. Mary, far from reaching for anything forbidden accepts her intense suffering at the foot of the cross as the Queen Mother, the Bride.
The Priesthood of Adam, Melchizedek and David is completed in the Messiah and He can then pass it on to those He had chosen. He even gave them the Sacrifice they were to offer; Himself.