God's fire is spiritual and corrective, what better example then Gehenna and espeicially The Lake of Divine Purging. Yes the fires in the OT toward the disobedient or misinformed people who did not do the right thing; there earthy body was gone, burnt up; but always their spirit returns to God who gave it.
Ecclesiastes 12:7
Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.
What I am saying to you is figuratively, or by using the scriptural symbolic language found in both NT and OT. Or another word examples point to what God’s Word is declaring about Gehenna or the Lake of Fire; (by the way I already said I cannot link these two places in scripture) let us not ask believe and trust the established; but reached out to what God’s Word is saying.
1 Corin 10:11 Now all these things happened unto them for examples: and they are written for our admonition, upon whom the ends of the world (age) are come.
Matthew 5:22
But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell (Gehenna) fire.
The below listed verse are good reference to Gehenna
Isaiah 30:33
Topheth has long been prepared; it has been made ready for the king. Its fire pit has been made deep and wide, with an abundance of fire and wood; the breath of the LORD, like a stream of burning sulfur, sets it ablaze.
The breath of the Lord (the spirit of the Lord) like a stream of burning sulfur (same as brimstone) which was used for purification (total symbolic language) Wood speaks of carnal nature (wood/hay stubble)
Jeremiah 7:31-32
They have built the high places of Topheth in the Valley of Ben Hinnom to burn their sons and daughters in the fire—something I did not command, nor did it enter my mind. So beware, the days are coming, declares the LORD, when people will no longer call it Topheth or the Valley of Ben Hinnom, but the Valley of Slaughter, for they will bury the dead in Topheth until there is no more room.
Here Gehenna is established as a place of burning dead bodies/rubbish and Gehenna is located just outside of the gate of Jersalem.
Jeremiah 19:13-15
The houses in Jerusalem and those of the kings of Judah will be defiled like this place, Topheth—all the houses where they burned incense on the roofs to all the starry hosts and poured out drink offerings to other gods.' "
Jeremiah then returned from Topheth, where the LORD had sent him to prophesy, and stood in the court of the LORD's temple and said to all the people, "This is what the LORD Almighty, the God of Israel, says: 'Listen! I am going to bring on this city and the villages around it every disaster I pronounced against them, because they were stiff-necked and would not listen to my words.' "
That is Gehenna Judgment that Jesus came and warned Isreal about.
Matthew 23:29-39
"Woe to you, teachers of the law and Pharisees, you hypocrites! You build tombs for the prophets and decorate the graves of the righteous. And you say, 'If we had lived in the days of our forefathers, we would not have taken part with them in shedding the blood of the prophets.' So you testify against yourselves that you are the descendants of those who murdered the prophets. Fill up, then, the measure of the sin of your forefathers!
"You snakes! You brood of vipers! How will you escape being condemned to hell (Gehenna)? Therefore I am sending you prophets and wise men and teachers. Some of them you will kill and crucify; others you will flog in your synagogues and pursue from town to town. And so upon you will come all the righteous blood that has been shed on earth, from the blood of righteous Abel to the blood of Zechariah son of Berekiah, whom you murdered between the temple and the altar. I tell you the truth, all this will come upon this generation.
"O Jerusalem, Jerusalem, you who kill the prophets and stone those sent to you, how often I have longed to gather your children together, as a hen gathers her chicks under her wings, but you were not willing. Look, your house is left to you desolate.For I tell you, you will not see me again until you say, 'Blessed is he who comes in the name of the Lord.'
Jeremiah 7:33-34
" 'The people of Judah have done evil in my eyes, declares the LORD. They have set up their detestable idols in the house that bears my Name and have defiled it. They have built the high places of Topheth in the Valley of Ben Hinnom to burn their sons and daughters in the fire—something I did not command, nor did it enter my mind. So beware, the days are coming, declares the LORD, when people will no longer call it Topheth or the Valley of Ben Hinnom, but the Valley of Slaughter, for they will bury the dead in Topheth until there is no more room. Then the carcasses of this people will become food for the birds of the air and the beasts of the earth, and there will be no one to frighten them away. I will bring an end to the sounds of joy and gladness and to the voices of bride and bridegroom in the towns of Judah and the streets of Jerusalem, for the land will become desolate.
Do you see it? This is the Judgment of Gehenna against Israel and all who persist in unbelief. However; although this happens it is not the end. God through Jesus, is restoring Israel, but not the natural nation but a spiritual nation of all mankind. All have sinned, none are righteous, no not one. All have been disobedient and therefore mercy is over them all.