First, notice that the Scripture does not say that any person is being burned by the “flaming fire.” It declares how the Lord's presence would be revealed.​

The fire is a symbol. Look at Zephaniah 3:8, 9 (NASB), “Therefore wait for Me,” says the LORD, “Until the day I rise up for plunder; My determination is to gather the nations to My assembly of kingdoms, to pour on them My indignation, all My fierce anger; All the earth shall be devoured with the fire of My jealousy. For then I will restore to the peoples a pure language, that they all may call on the name of the LORD, to serve Him with one accord.”​

We see that first comes the fire (of God’s jealousy), then He restores to the people a pure language. The fire is the intensity of God’s judgment against the evil systems. It does not burn the people, because then they would either be destroyed or tormented beyond recovery. Even now, the world is experiencing fiery troubles. After the present evil systems are destroyed, the human race will be ready to hear and learn God’s righteous plan for all mankind. Daniel 2:44 (RSV), "in the days of those kings the God of heaven will set up a kingdom which shall never be destroyed, nor shall its sovereignty be left to another people. It shall break in pieces all these kingdoms and bring them to an end, and it shall stand forever.”

Scriptures foretell that all mankind will learn about God. The “pure language” of Zephaniah is just one citation. Jeremiah 31:34, “they shall teach no more every man his neighbor, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.” Jeremiah 31:34. 

God will establish His righteous reign in Jerusalem (Isaiah 2: 2-4) and all mankind will eagerly seek Him there. Zechariah 8:22,23, "many peoples and powerful nations will come to Jerusalem to seek the LORD Almighty and to entreat him…the LORD Almighty says: ‘In those days ten people from all languages and nations will take firm hold of one Jew by the hem of his robe and say, Let us go with you, because we have heard that God is with you.’ ”

These verses, and many more, describe the Kingdom for which we all pray, "Thy kingdom come; thy will be done on earth, even as it is in heaven.” At the end of Christ's reign, all mankind will have learned about and experienced the true love of God. Any who refuse to accept these blessings would then deserve the “everlasting destruction” spoken of in 2 Thessalonians 1:9.