“it is the building that is burning and by burning is purified of straw and stubble”
Except Paul’s point has NOTHING to do with purification. His word picture has a simple lesson: “But each man must be careful how he builds on it.”
It is a warning to the folks who claim to be wise, but who are confusing the church:
Chapter 1:
“12 Now I mean this, that each one of you is saying, ‘I am of Paul,’ and ‘I of Apollos,’ and ‘I of Cephas,’ and ‘I of Christ.’ 13 Has Christ been divided? Paul was not crucified for you, was he? Or were you baptized in the name of Paul?”
Chapter 2:
“And when I came to you, brethren, I did not come with superiority of speech or of wisdom...3 I was with you in weakness and in fear and in much trembling, 4 and my message and my preaching were not in persuasive words of wisdom, but in demonstration of the Spirit and of power, 5 so that your faith would not rest on the wisdom of men, but on the power of God.”
Chapter 3:
“4 For when one says, ‘I am of Paul,’ and another, ‘I am of Apollos,’ are you not mere men?
5 What then is Apollos? And what is Paul? Servants through whom you believed, even as the Lord gave opportunity to each one. 6 I planted, Apollos watered, but God was causing the growth. 7 So then neither the one who plants nor the one who waters is anything, but God who causes the growth...
...So then let no one boast in men. For all things belong to you, 22 whether Paul or Apollos or Cephas...”
Chapter 4:
“6 Now these things, brethren, I have figuratively applied to myself and Apollos for your sakes, so that in us you may learn not to exceed what is written, so that no one of you will become arrogant in behalf of one against the other...
...18 Now some have become arrogant, as though I were not coming to you. 19 But I will come to you soon, if the Lord wills, and I shall find out, not the words of those who are arrogant but their power. 20 For the kingdom of God does not consist in words but in power. 21 What do you desire? Shall I come to you with a rod, or with love and a spirit of gentleness?”
The first 4 chapters of 1 Cor deals with the divisions in the church. And Paul makes it clear that there should be none, because any human is supposed to be working for God and under God, and it is God who provides the growth.
But he does give a warning to those at Corinth:
“I laid a foundation, and another is building on it. But each man must be careful how he builds on it. 11 For no man can lay a foundation other than the one which is laid, which is Jesus Christ. 12 Now if any man builds on the foundation with gold, silver, precious stones, wood, hay, straw, 13 each man’s work will become evident...
18 Now some have become arrogant, as though I were not coming to you. 19 But I will come to you soon, if the Lord wills, and I shall find out, not the words of those who are arrogant but their power. “
I deal with the text. The text describes purification followed by salvation. Write your own epistle if you want to make a different point.