Hebrews 7:3, 15, 17, 21

Without [any record of] father or mother, nor ancestral line, without [any record of] beginning of days (birth) nor ending of life (death), but having been made like the Son of God, he remains a priest without interruption and without successor.

And this becomes even more evident if another priest arises in the likeness of Melchizedek, [Ps 110:4]

For it is attested [by God] of Him, “YOU (Christ) ARE A PRIEST FOREVER ACCORDING TO THE ORDER OF MELCHIZEDEK.” [Ps 110:4]

(for those Levites who formerly became priests [received their office] without [its being confirmed by the taking of] an oath, but this One [was designated] with an oath through the One who said to Him, “THE LORD HAS SWORN AND WILL NOT CHANGE HIS MIND or REGRET IT, ‘YOU (Christ) ARE A PRIEST FOREVER’ ”). [Ps 110:4]