Hebrews 7:11-17

Now if perfection [a perfect fellowship between God and the worshiper] had been attained through the Levitical priesthood (for under it the people were given the Law) what further need was there for another and different kind of priest to arise, one in the manner of Melchizedek, rather than one appointed to the order of Aaron? For when there is a change in the priesthood, there is of necessity a change of the law [concerning the priesthood] as well. For the One of whom these things are said belonged [not to the priestly line of Levi but] to another tribe, from which no one has officiated or served at the altar. For it is evident that our Lord descended from [the tribe of] Judah, and Moses mentioned nothing about priests in connection with that tribe. And this becomes even more evident if another priest arises in the likeness of Melchizedek, [Ps 110:4] who has become a priest, not on the basis of a physical and legal requirement in the Law [concerning his ancestry as a descendant of Levi], but on the basis of the power of an indestructible and endless life. For it is attested [by God] of Him, “YOU (Christ) ARE A PRIEST FOREVER ACCORDING TO THE ORDER OF MELCHIZEDEK.” [Ps 110:4]