This is too long a passage to print here,
and is a lot to dissect, thus I will only bring out the highlights.
Verses 18-19 rather sums it up:
out with the old and in with the new!
"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,
One purpose of parenting is to bring the outward constraints (No! No!) into inward constraints so that the child will become an adult making good decisions apart from the parent. It would be awkward indeed to chase around a young adult saying, "No, No! Bad boy!" But oh how the parent suffers when the grown child makes decisions that are contrary to how they were raised. Yep. God knows that feeling. Yet He, as the divine and perfect parent, has the ability to go beyond what we can do. Not only did His only begotten become the sacrifice, but He has offered His very own self, a part of the Trinity, the Holy Spirit, to live in us. Jesus opened the way as our high priest and the Spirit can take us there into the holy of holies, into the presence of God where no outward constraints are needed (the law), only the inward (the Spirit).
The Jewish Christians perfectly understood this passage of the epistle, certainly better than we are able. Yet it was contrary to how they were taught growing up as good little Jews.
At first it talks about how Melchizedek was greater because Abraham paid tithe to him from the choice spoils of war (verse 4). "Without any dispute the lesser is blessed by the greater." (verse 7) (I won't even mention how it speaks to us today about tithing a tenth of our income, which is a chunk of change at tax return time if you get money back like we do.)
We need to keep in mind that the law was given before the priesthood: think Moses throwing down the ten commandments carved in stone, that they were both physically and sinfully broken. All the kings' and priests' men could not put Humpty, I mean, the law back together again. It was given to show that something greater was needed, not a popular discussion to have with a Jew. "Now if perfection was through the Levitical priesthood...what further need was there for another priest to arise..." (verse 11) This is referring to the one God swore would be a priest forever in Psalm 110:4, the whole of which is prophetic of the coming Messiah speaking of Him as a king and a priest.
Now here is the kicker. "For when the priesthood is changed, of necessity there takes place a change of law also." (verse 12) Thus, like Melchizedek not being in the priestly line because he came before the giving of the law and the instructions for the priesthood, so Christ should not qualify because he is of the line of Judah, not of the tribe of Levi. This is enough to make a good Jew nervous when we start messing with the law and the priesthood talking about change!
But we are coming to the good part, the whole reason Melchizedek is brought up as indisputable evidence to the Jews. He wasn't part of the priestly line, but was greater than Abraham. "For on the one hand, there is a setting aside of a former commandment because of its weakness and uselessness...(verse 18) "(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.'" In other words, God made the rules, He can change the rules concerning the priesthood. However, when He ordained His Son as a priest, He swore that it would never change.
Adam Clarke says, "...the Levitical priesthood and the law of Moses, being established without an oath, were thereby declared to be changeable at God's pleasure...The everlasting priesthood of Christ with an oath, to show that the Gospel dispensation should never be changed, and never be abolished...The Lord sware, to show the immutability of His counsel, and will not repent--can never change His mind nor purpose, 'Thou art a priest for ever'--as long as time shall run."
He goes on concerning verse 18, "'weakness and uselessness...' it had no Spirit to minister; it required perfect obedience, but furnished not assistance to those who were under it. No man was benefited by the mere observance of its precepts: it pardoned no sin, changed no heart, reformed no life; it found men dead in trespasses and sins, and it consigned them to eternal death'...'For the law made nothing perfect' It completed nothing; it was only the outline of a great plan, the shadow of a glorious substance. It neither pardoned sin, nor purified the heart, nor gave strength to obey the moral precepts...This went before to prepare the way of the Lord; to show the exceeding sinfulness of sin, and the strict justice of God."
"'The better hope' founded on the priesthood and atonement of Christ, was afterwards introduced for the purpose of doing what the law could not do, and giving privileges and advantages the law would not afford. One of these privileges immediately follows:--'By which we draw nigh unto God.' But through Christ, as our high priest, all believers in Him have an entrance to the holiest by His blood."
As John Wesley says of verse 19, "'By which we draw nigh to God'--Yea, so nigh as to be one Spirit with Him. And this is true perfection."
Andrew Murray says, "Draw nigh to God! Nothing but this can satisfy God and His love. He longs to have His children come to dwell in that love, and to delight in His presence. He sent His Son to bring us to Him...Man was created for the presence of God...by His Holy Spirit to make the drawing nigh to God our continual abiding experience."
This is the better hope. This is good news indeed!
So hang on, you Jewish converts,
don't fall back under the law.
So hang on, you Gentiles,
Christ opened the way to the holiest of holies,
not just to Jews, but to Gentiles as well,
"For God so loved the world,
that He gave His only begotten Son..."