Melchizedek king of Salem (ancient Jerusalem) brought out bread and wine [for them]; he was the priest of God Most High.

The Lord has sworn [an oath] and will not change His mind:
“You are a priest forever
According to the order of Melchizedek.”

just as He also says in another place,

“You are a priest [appointed] forever
According to the order of Melchizedek.”

being designated by God as High Priest according to the order of Melchizedek.

where Jesus has entered [in advance] as a forerunner for us, having become a High Priest forever according to the order of Melchizedek.

For this Melchizedek, king of Salem, priest of the Most High God, met Abraham as he returned from the slaughter of the kings and blessed him,

Furthermore, here [in the Levitical priesthood] tithes are received by men who are subject to death; but in that case [concerning Melchizedek], they are received by one of whom it is testified that he lives on [perpetually].

for Levi was still in the loins (unborn) of his forefather [Abraham] when Melchizedek met him (Abraham).

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?

And this becomes even more evident if another priest arises in the likeness of Melchizedek,

For it is attested [by God] of Him,

“You (Christ) are a Priest forever
According to the order of Melchizedek.”

(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’”).