What you are not understanding is that actually not a letter of the law will pass for those still in the old covenant. All promises to the house of Israel including those in
Heb. 8 are still unfulfilled until the end of the time if the gentiles. But none of the law applies to the Christian (
Gal. 3).
All OT scripture is Christological and teaches us why we need Christ. However, the audience was always Israel. Jesus preached to the Jews first (
Rom. 1:16) so most of the pre crucifixion scriptures emphasize teachings to them.
Matt.5 is a perfect example. The terms of the new covenant in blood for the Christians began at the time of the crucifixion and resurrection. This covenant of blood has its own terms including Jesus as our sabbath rest. So find a post crucifixion verse that requires the Christian to keep the old covenant 4th commandment.
There is no Scripture that says Jesus turned into the 4th commandment so we do not need to keep it.
Mat5:17 Jesus told us He
did not come to destroy the law but to
fulfill.
What prophecy did Jesus fulfill
Isa 42:21 The LORD is well pleased for his righteousness' sake;
he will magnify the law, and make it honourable.
The definition for the word He used to magnify His law
gâdal
gaw-dal'
A primitive root; properly to twist (compare H1434), that is, to be (causatively make)
large (in various senses, as in body, mind, estate or honor, also in pride): -
advance, boast,
bring up, exceed, excellent, be (-come, do, give, make, wax),
great (-er, come to . . estate, + things),
grow (up),
increase,
lift up, magnify (-ifical), be much set by, nourish (up), pass, promote, proudly [spoken], tower.
But sadly people twist this into the opposite, that He came to end the law, when Jesus so plainly said the opposite
18 For assuredly, I say to you, t
ill heaven and earth pass away, one [b]jot or one [c]tittle will by no means pass from the law till all is fulfilled.
Heaven and earth are still here, and not all is fulfilled like:
Mat 24:34 Verily I say unto you,
This generation shall not pass, till all these things be fulfilled.
Jesus did not destroy all the prophecies in the Book of Mat 24 or Isaiah or Revelation or Daniel etc, that has yet to be fulfilled, therefore not a jot or tittle shall pass from the law
Why He said plainly
19
Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven; but whoever does and teaches
them, he shall be called great in the kingdom of heaven.
According to the next verse least in heaven means not there.
Jesus went on to fulfill the prophecy in Isa42:21 to show what it means to magnify His laws which means make greater, not smaller
21
“You have heard that it was said to those [d]of old, ‘You shall not murder, and whoever murders will be in danger of the judgment.’ 22
But I say to you that whoever is angry with his brother [e]without a cause shall be in danger of the judgment. And whoever says to his brother, ‘Raca!’[
f] shall be in danger of the council. But whoever says, [
g]‘You fool!’ shall be in danger of [
h]hell fire. 23 Therefore if you bring your gift to the altar, and there remember that your brother has something against you, 24 leave your gift there before the altar, and go your way. First be reconciled to your brother, and then come and offer your gift. 25 Agree with your adversary quickly, while you are on the way with him, lest your adversary deliver you to the judge, the judge hand you over to the officer, and you be thrown into prison. 26 Assuredly, I say to you, you will by no means get out of there till you have paid the last penny.
Jesus is teaching the heart of the issue, why He wrote His laws in the heart because if the heart is changed thou shalt not murder would automatically be kept. This applies to all of the commandments why Jesus said plainly not to break or teach others to break the least of these commandments and they apply to all Ten because God wrote Ten Commandments, no any other number Deut4:13 Exo34:28 heaven and earth are still here, sin is still in the world, therefore so is God's holy and eternal laws the way He said. Exo31:18
If we are breaking the letter of the law its impossible to be walking in the Spirit. Paul contrasts this several times - not being subject to the law of God is the carnal mind Rom8:7-8 the spiritual mind has the righteousness of the law fulfilled in us where no one would be worshipping another god, or using His name in an unholy manner, or bowing to images, or breaking His holy Sabbath day, or stealing or lying or breaking the least of these just as Jesus said. Mat5:19