Elijah is at Mt. Carmel and challenges the prophets of Baal in a duel to publically display that the LORD God is the only true God. Elijah makes a proposal to the people (2 Kings. 18.24):
And you call upon the name of your god, and I will call upon the name of the LORD, and the God who answers by fire, he is God.” And all the people answered, “It is well spoken.”
It was Elijah’s suggestion but the people agreed: The God/god who answered with fire would prove himself to be the real God.
We know the story: after much time and desperation it is evident that Baal is not going to answer. He is a false god.
Elijah however starts his part in the duel by drenching the slaughtered bull, that the fire is supposed to consume, in water and thus making it utterly impossible to set the altar and the sacrifices on fire by human means.
When Elijah prays to the LORD, fire does come from heaven and consumes, not only the bull but also the water, the wood and even the stones!
This axiom, stated by the prophet Elijah and universally agreed upon by his enemies, that “the God who answers by fire, he is God”, still stands today.
Paul writes to Timothy (1 Tim. 3:16):
Beyond all question, the mystery of godliness is great:
He appeared in a body,
was vindicated by the Spirit,
was seen by angels,
was preached among the nations,
was believed on in the world,
was taken up in glory.
How did the Spirit vindicate Jesus? Romans 8:9-11:
You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him. But if Christ is in you, although the body is dead because of sin, the Spirit is life because of righteousness. If the Spirit of him who raised Jesus from the dead dwells in you, he who raised Christ Jesus from the dead will also give life to your mortal bodies through his Spirit who dwells in you.
The Spirit was freely given to Christians on the day of Pentecost in the shape of fire (Acts 2:1-4)
When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.
This was the same Spirit that raised Jesus from the dead, and so proved him to be the son of God, and totally righteous.
Fire from heaven proved who is the only true God on the day of Pentecost. And we know His power still today.