Hebrews 7

For this Melchizedek, king of Salem, priest of the Most High God, who met Abraham as he was returning from the slaughter of the kings and blessed him, to whom also Abraham apportioned a tenth part of all the spoils, was first of all, by the translation of his name, king of righteousness, and then also king of Salem, which is king of peace.

So, this high priest, Melchizedek, is called king of righteousness and king of peace.

Without father, without mother, without genealogy, having neither beginning of days nor end of life, but made like the Son of God, he remains a priest perpetually.
Now observe how great this man was to whom Abraham, the patriarch, gave a tenth of the choicest spoils.

And those indeed of the sons of Levi who receive the priest's office have commandment in the Law to collect a tenth from the people, that is, from their brethren, although these are descended from Abraham.

But the one whose genealogy is not traced from them collected a tenth from Abraham and blessed the one who had the promises.

Abraham gives his tithe to one who is not of the Levites. When I first heard this story, I didn't know who the Levites were! But now I know why this is important. It's a reminder that the priests aren't Gods. the great Jewish patriarch didn't (couldn't) give his tithe to the priests descended from Levi.

But without any dispute the lesser is blessed by the greater.

In this case mortal men receive tithes, but in that case one receives them, of whom it is witnessed that he lives on. And, so to speak, through Abraham even Levi, who received tithes, paid tithes, for he was still in the loins of his father when Melchizedek met him.

Now if perfection was through the Levitical priesthood (for on the basis of it the people received the Law), what further need was there for another priest to arise according to the order of Melchizedek, and not be designated according to the order of Aaron?

For when the priesthood is changed, of necessity there takes place a change of law also.

For the one concerning whom these things are spoken belongs to another tribe, from which no one has officiated at the altar.

For it is evident that our Lord was descended from Judah, a tribe with reference to which Moses spoke nothing concerning priests. And this is clearer still, if another priest arises according to the likeness of Melchizedek, who has become such not on the basis of a law of physical requirement, but according to the power of an indestructible life.

There's a lot in the preceding passages, but the most important part is the basis which is being layed for the new High Priest - the theological foundation from the Jewish tradition itself pointing to Jesus as priest and sacrifice.

For it is attested of Him,
"YOU ARE A PRIEST FOREVER '
ACCORDING TO THE ORDER OF MELCHIZEDEK."

For, on the one hand, there is a setting aside of a former commandment because of its weakness and uselessness (for the Law made nothing perfect), and on the other hand there is a bringing in of a better hope, through which we draw near to God.

"for the law made nothing perfect" Whoa. I can't believe I read that! But I thought the 10 commandments could save my soul!

Ok, Ok. I didn't really think that, but I knew mostly of the things I shouldn't do rather than the promises of God.

And inasmuch as it was not without an oath (for they indeed became priests without an oath, but He with an oath through the One who said to Him,
"THE LORD HAS SWORN
AND WILL NOT CHANGE HIS MIND,
'YOU ARE A PRIEST FOREVER'");

so much the more also Jesus has become the guarantee of a better covenant.

The former priests, on the one hand, existed in greater numbers because they were prevented by death from continuing, but Jesus, on the other hand, because He continues forever, holds His priesthood permanently.

Therefore He is able also to save forever those who draw near to God through Him, since He always lives to make intercession for them.

For it was fitting for us to have such a high priest, holy, innocent, undefiled, separated from sinners and exalted above the heavens; who does not need daily, like those high priests, to offer up sacrifices, first for His own sins and then for the sins of the people, because this He did once for all when He offered up Himself.

For the Law appoints men as high priests who are weak, but the word of the oath, which came after the Law, appoints a Son, made perfect forever.