So... it seems that you don't consider the New Testament as Scripture. If you did, then you'd realize that the Holy Spirit DID KNOW that the writings were Scripture, and that the words of Paul, SCRIPTURE, are applicable regardless whether he knew them to be or not, and are, therefore, applicable. However, I do not believe that Paul did not know he was penning Scripture, given the number of times he directed folks to heed his commands, examples, and doctrines. In any case, it makes no matter whether he did or not. Unless you don't accept his writings as Scripture.
The New Testament is Scripture.
But the reason it is Scripture is because our tradition says it is so.
When Paul was writing his letters, the Holy Spirit no doubt knew that this would be Scripture, but Paul himself certainly didn't know what would appear in all of the Gospels. He wasn't an eyewitness to Jesus' life, and the Gospels hadn't been written yet.
Within Scripture, there is always the problem of the later-in-time. After all, Deuteronomy and Leviticus give the explicit rules for divorce, right there in the Torah. Jesus says divorce was NEVER God's law, and that the rules of divorce are a tradition of Moses (even though they are in the Scripture). Jesus does this quite a bit in Matthew, saying 'Scripture says...but I say...'.
An example is the matter of unclean foods. Scripture certainly DOES list a whole list of unclean foods.
Later, Jesus says that NO FOOD makes you unclean.
So, EITHER the older Scripture, in the Torah, of the food rules is another case of Jewish TRADITION being recorded in the Scriptures and departing from God's actual Law (like Jesus says divorce is), OR the Scripture really WAS inspired by God to say those foods were impure, but God later overturns the rule of old scripture and puts a new rule down.
Unfortunately, this plays havoc with Jesus' assertion, in Matthew, that 'not a jot nor a tittle of the law shall be changed'. Either Jesus then changes the law in spite of himself...OR he is changing something in the Scripture that ISN'T really law, and is identifying parts of what is traditionally viewed as "Scripture" which should no longer be treated as Scripture. Example: the Mosaic law of divorce. Jesus said that wasn't God's rule from the beginning. He says what the right rule is. So, did Jesus CHANGE Scripture (contrary to what he said he wasn't doing), or is that part of traditional "Scripture" not really Scripture after all? Ditto for the food and purity rules.
More to your point, The Old Testament gives one rule, and Jesus gives a different rule. If, as I expect you would assert, BOTH are Scripture, and it's wrong to sequence Scripture, then who's right, Moses or Jesus?
I have to answer Jesus, because he's God incarnate, according to Scripture, and that settles all dispute.
The Holy Spirit knew, when he was inspiring Matthew, Mark, Luke and John, that people would read words that said "And Jesus said..." and believe that. That's why the Holy Spirit took such care to make sure that there are four separate, parallel recountings of Jesus' ministry in the Bible, to give the testimony from four different viewpoints, and hammer home the authenticity of Jesus' words. The Holy Spirit intended for the Bible, where it reads, "And Jesus said..." to be taken literally that Jesus, Son of God and the Word Incarnate, said that. On the strength of THAT how could anyone hold up a piece of the Torah against Jesus and say that the Torah was right and Jesus wrong?
It is nonsensical.
The Holy Spirit was the Author of the whole thing, and the Author wrote HIMSELF into the story in the Gospels, and put words in the mouth of God, via the pens of the inspired writers.
How, then, can Jesus not be taken most literally when he says thus and so?
It makes no sense to do otherwise!
Jesus says clearly what one must DO, and what one must BELIEVE. Paul SEEMS TO SAY at one point that all that matters is what you believe, but James says the opposite, the whole Old Testament says the opposite, and most importantly of all, JESUS says the opposite. Certainly, whatever the Holy Spirit was intending to do through the pen of Paul, it was NOT to try and contradict, countermand or limit Jesus!
Paul has to be read in light of Jesus, obviously.
It can't be the other way around.
It would make no sense at all for God to enter into the story and teach in person, and for a later person to enter into the story and countermand God. Paul never explicitly does this, of course. Paul is a good man. But Paul's words are sometimes taken literally in a way that they cannot be. Faith alone, without anything else, 'faith without works', might SEEM to be what Paul teaches somewhere, but that can't be read that way. It can't be what it means. It contradicts James' "Faith without works is dead", and it contradicts Jesus' whole life and teachings. Jesus isn't all about "believe this, believe that". He's very much a "DO this and DO that" kind of guy.
Paul has to be understood to mean that faith is what is needed, but the one who has faith will inevitably DO those things that faith requires be done, to the extent he can.
And the one thing lacking in Jesus is a focus on Scripture. Jesus certainly talks about Scripture, to a degree. Almost all of his actual citations to Scripture are from the Law and the Prophets. And in many cases, he corrects scripture. The Son of Man is also the God of the Scriptures, and what came before him, notably the Torah, is actually IMPERFECT if read alone, because the Bible itself contains the traditions of men IN the Scriptures. To get the Torah right, you have to read Jesus, who corrects and amends certain things about the Torah.
And then Jesus doesn't leave a book himself. He leaves some practices, a summary of the law in the two great commandments, and a group of men commissioned to do the work.
When you said this: "So... it seems that you don't consider the New Testament as Scripture. If you did, then you'd realize that the Holy Spirit DID KNOW that the writings were Scripture," you were addressing me and my belief directly. Now I will address yours directly. It seems that you consider your non-Scriptural tradition of what is "Scripture" to itself be divinely inspired, so that you can confidently say that the New Testament IS Scripture. The New Testament does not define itself as Scripture. It doesn't define itself at all. Somebody had to compile that list of documents, accepting some and rejecting others, to determine what "Scripture" was. The Bible doesn't say how to do that, or who is to do it. To the extent you are certain that the early Church got it right, through all of those vicissitudes, is the extent to which you are admitting, however unwittingly, that the Holy Spirit has made authoritative decisions and revelations OUTSIDE OF Scripture. To the extent you are unwilling to make that allowance, then how do you know what "Scripture" IS? Scripture doesn't say.
But within Scripture itself, there are different people speaking and saying different things, and who is speak