Hebrews 7:20-22

And indeed it was not without the taking of an oath [that Christ was made priest] (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] And so [because of the oath’s greater strength and force] Jesus has become the certain guarantee of a better covenant [a more excellent and more advantageous agreement; one that will never be replaced or annulled].