Deuteronomy 4:24

[Daniel 7:9] "I beheld until thrones were set up, and the Ancient of days took His seat. His garment was as white as snow, and the hair of His head was like pure wool. His throne was composed of fiery flames and its wheels were set on fire. From before His presence there issued forth a rushing, fiery stream." We read something similar in John's Apocalypse: "After these things I was immediately in the Spirit, and lo, a throne was set up in heaven, and one was seated upon the throne; and He who sat upon it had the likeness of jasper and sardine stone, and there was a rainbow round about the throne like the appearance of emerald. Around the throne there were twenty-four other thrones, and upon the twenty-four thrones there sat twenty-four elders, clothed in shining garments; upon their heads was a golden crown, and lightning flashes issued from the throne, and voices and thunder. And in front of the throne there were seven torches of burning fire, which were the seven spirits of God. And in front of the throne lay a glassy sea like unto crystal." (Revelation 4:2-6) And so the many thrones which Daniel saw seem to me to be what John called the twenty-four thrones. And the Ancient of days is the One who, according to John sits alone upon His throne. Likewise the Son of man, who came unto the Ancient of days, is the same as He who, according to John, is called the Lion of the tribe of Judah, the Root of David, and the titles of that sort (Revelation 5:5). I imagine that these thrones are the ones of which the Apostle Paul says, "Whether thrones or dominions..." (Colossians 1:16). And in the Gospel we read, "Ye yourselves shall sit upon twelve thrones, judging the twelve tribes of Israel" (Matthew 19:28). And God is called the One who sits and who is the Ancient of days, in order that His character as eternal Judge might be indicated. […]

If God is fire, he is fire in order to drive out the cold of the devil.

"God is spirit, and those who worship him should worship in spirit and in truth." Our God is also "a consuming fire." Therefore God is called by two names: "spirit" and "fire." To the just he is spirit; to sinners he is fire.

Hear what is written: "Our God is a consuming fire." What does the God of fire consume? Will we be so senseless as to think that God consumes the firewood or straw or hay? But the God of fire consumes human sins. He consumes them, devours them, purges them, as he says in another place, "I will purge you with fire for purity."

And the Holy Spirit descended upon the holy apostles in the form of fire, because he is God, and "God is a consuming fire."