Luke 3:16 John answered them all, "I baptize you with water; but he who is mightier than I is coming, the thong of whose sandals I am not worthy to untie; he will baptize you with the Holy Spirit and with fire.

It’s a hot potato. If you can’t stand the heat, get out of the kitchen. Where there is smoke, there is fire. He who plays with matches is liable to get burned. Lots of sayings, and all basically tell us that the goal of life is to be a cool customer, and that heat is something we want to avoid.

So if Jesus is going to baptize us with the Holy Spirit and with fire, then we focus on the water of baptism and the strictly symbolic fire, a reminder of the outpouring of the Spirit on Pentecost. We have no trouble with the spirit being poured out on all people, not even with the Spirit being in us, in our hearts, which by grace through faith is the temple of God. We like to remember the peace of God which passes all understanding, and at least in part, coming to church is something we do to restore the peace in our lives.

But our text tells us that the fire of baptism is not merely symbolic.

Luke 3:17 His winnowing fork is in his hand, to clear his threshing floor, and to gather the wheat into his granary, but the chaff he will burn with unquenchable fire."
Luke 9:54 And when his disciples James and John saw it, they said, "Lord, do you want us to bid fire come down from heaven and consume them?"
So fire serves 2 purposes, judgement and purification. For while water can wash away most of the dirt, it can’t do anything for the trapped in dirt, and that’s why mothers keep telling their children to use the soap, not the towel, for soap helps remove the stubborn dirt. But if its really trapped in, even soap is not enough. When you purify iron, or silver or gold, you use fire. Fire burns away the impurities and leaves the good metal. Fire is the sort of thing which God uses to reveal to us the sort of metal, that is our faith, which is in us.

Mal 3:2 But who can endure the day of his coming, and who can stand when he appears? "For he is like a refiner's fire and like fullers' soap;
Or to go back to the text, God is willing to gather in the grain, but he has no room to save or to store the chaff. Or, quite simply, being a Christian is not always comfortable. For as we grow in faith, sometimes things get hot, for all through life God is working to purify us, so that we may be wholly the children of God, no longer a mixture of saint and sinner, but this process of sanctification means that over time God is working to remove the sin, and the sinful desires from our lives. You see, at baptism, our salvation is accomplished in an instant, and we receive in an instant, forgiveness of sins, but our sanctification, the purification of our lives is ongoing; it is part of how we are growing in faith. So as we read further in the Gospel we hear:

Luke 12:49 "I came to cast fire upon the earth; and would that it were already kindled!
Luke 22:55 and when they had kindled a fire in the middle of the courtyard and sat down together, Peter sat among them.
Jesus suffering and death would really be a trial by fire for the disciples. Judas would be shown to be lacking, and perish; Peter would be shown to be weak, but that through contrition and repentance God would work not only forgiveness, but a measure of purification, and that through it all he would grow in faith. But what is more, God doesn’t want us to be surprised by fire, or that the life of a Christian is not always peaceful, but God does always want us to know that it will work for our good. God wants us to know that he will be with us, and that his grace is sufficient.

Isa 43:2 When you pass through the waters I will be with you; and through the rivers, they shall not overwhelm you; when you walk through fire you shall not be burned, and the flame shall not consume you.

God also want us to know that he is at work in our lives, and that the story of his work in and among us is a story that must be told:
 Jer 20:9 If I say, "I will not mention him, or speak any more in his name," there is in my heart as it were a burning fire shut up in my bones, and I am weary with holding it in, and I cannot.
Our Christian life may begin in the waters of baptism, but that is not the rest of the story.