One fire, and the God it reveals
The Fire on Sinai
Three months out of Egypt, Israel camps before a mountain, and the mountain is on fire. Exodus 19:18 says that Sinai was completely in smoke because the Lord descended upon it in fire, and the smoke went up like the smoke of a furnace, and the whole mountain quaked greatly. This is not the gentle flame of the burning bush or the guiding light of the pillar. This is fire that makes the ground tremble and warns the people to keep their distance. Here fire is holiness that cannot be approached casually. God draws near to make a covenant and to give his law, and the manner of his coming teaches its own lesson before a single commandment is spoken. Boundaries are set around the mountain. The people are told not to touch it. Deuteronomy 4:24 later sums up what Sinai revealed: that the Lord is a consuming fire. To meet such a God is a serious thing, and the fire says so.
“And mount Sinai was altogether on a smoke, because the LORD descended upon it in fire: and the smoke thereof ascended as the smoke of a furnace, and the whole mount quaked greatly.”Exodus 19:18
“For the LORD thy God is a consuming fire, even a jealous God.”Deuteronomy 4:24
The fire in Scripture
The setting is Exodus chapter 19. Israel arrives at Sinai and God calls Moses up to establish the terms of the covenant. In the days before God descends, the people are told to consecrate themselves and wash their clothes, and in Exodus 19:12 and 19:13 strict limits are set around the mountain, so that anyone who touches it is to die. The holiness of the coming encounter requires preparation and distance in advance. When the day comes, the phenomena are overwhelming. Exodus 19:16 describes thunders and lightnings, a thick cloud on the mountain, and a very loud trumpet blast, so that all the people in the camp trembled. Exodus 19:18 adds the fire and the smoke like a furnace, and the quaking of the whole mountain. In Exodus 19:19 the trumpet grows louder and Moses speaks, and God answers him by a voice. The scene is deliberately terrifying, arranged so that the people feel the weight of who is present. The people's reaction is recorded in Exodus 20:18 and 20:19, after the giving of the commandments. Seeing the thunder, the lightning, the trumpet, and the mountain smoking, they draw back and stand far off, and they beg Moses to speak with them himself rather than have God speak to them, lest they die. Moses answers in Exodus 20:20 that God has come to test them and that the fear of him may keep them from sinning. The fire produces exactly the reverence it was meant to produce. Moses looks back on this day repeatedly in Deuteronomy. He reminds the people in Deuteronomy 4:11 and 4:12 that the mountain burned with fire to the heart of heaven, and that they heard a voice but saw no form. Then, in Deuteronomy 4:24, he distills the meaning into a single statement: the Lord your God is a consuming fire, a jealous God. Later still, the letter to the Hebrews takes up this scene in Hebrews 12:18 through 21, recalling the fire, the darkness, the tempest, and the terror, and even Moses saying that he was exceedingly afraid. The memory of the burning mountain became a fixed point in Israel's understanding of what God is like.
What it comes to mean
The plainly stated meaning of the fire on Sinai is the seriousness of God's holiness. Exodus 19 does not leave this to inference. The boundaries, the warnings of death for touching the mountain, the fire, the smoke, and the quaking all say the same thing: the God who is giving this covenant is not to be approached lightly or on human terms. Deuteronomy 4:24 states it outright by calling him a consuming fire. The purpose of the fear is also stated, which guards against misreading. Moses tells the people in Exodus 20:20 that God has come to prove them, and that the fear of him should be before them so they will not sin. The terror is not cruelty and not an end in itself. It is meant to form a people who take God seriously and therefore take his commandments seriously. The fire is instructive; it presses the reality of God onto a nation freshly out of slavery.
How it points to Christ, who baptizes with the Spirit and fire
The letter to the Hebrews makes the connection to Christ explicit, so this link is a stated New Testament reading rather than something merely drawn out. Hebrews 12:18 through 24 sets Sinai directly against the new covenant. The writer says that believers have not come to a mountain that burned with fire, to darkness and tempest and a voice so terrible that the people begged it to stop. Instead, they have come to Mount Zion, to the city of the living God, and to Jesus the mediator of a new covenant, whose sprinkled blood speaks better things. The contrast is explicit and intentional. Yet Hebrews does not let the fire go. After holding up the greater access believers now have, it closes in Hebrews 12:28 and 12:29 by returning to Deuteronomy 4:24: our God is a consuming fire. The point is not that God has changed from holy to harmless, but that in Christ the way to approach the consuming fire has changed. What Sinai forbade, the mediator provides. The people who once could not touch the mountain are now invited to draw near, because another has stood in the fire on their behalf. This holds the two truths together honestly. Christ does not make God less holy; he makes the holy God approachable. The fire that kept Israel at a distance is the same holiness satisfied at the cross, so that believers come with reverence and godly fear, but they come. The burning mountain and the mediator are not rivals. One shows what God is, and the other shows how sinners may live in his presence and not be consumed.
Questions people ask
Was the fear at Sinai meant to drive people away from God?
No. Exodus 20:20 has Moses telling the people not to fear in one sense, because God came to prove them and to set the fear of him before them so they would not sin. The terror was formative, meant to make a redeemed people take God's holiness and his commandments with full seriousness.
If God is a consuming fire, how can anyone approach him?
Hebrews 12:18 through 24 answers this by contrasting Sinai with Mount Zion. Believers come not to the burning mountain but to Jesus, the mediator of a new covenant. Hebrews still calls God a consuming fire in 12:29, so his holiness is unchanged; what changed is that Christ provides the way to draw near without being consumed.