Fire is a frequently recurrent emblem of the Holy Spirit, both in the Old and New Testament. It is not the destructive, but the vitalising, glowing, transforming, energy of fire, which is expressed. The fervour of holy enthusiasm, the warmth of ardent love, the melting of hard hearts, the change of cold, damp material into its own ruddy likeness, are all set forth in this great symbol. John's water baptism was poor beside Messiah's immersion into that cleansing fire. Fire turns what it touches into kindred flame. The refiner's fire melts metal, and the scum carries away impurities. Water washes the surface, fire pierces to the centre. But while that cleansing by the Spirit's fire was to be Messiah's primary office, man's freedom to accept or reject such blessing necessarily made His work selective, even while its destination was universal. So John saw that His coming would part men into two classes, according as they submitted to His baptism of fire or not. The homely image of the threshing-floor, on some exposed, windy height, carries a solemn truth. The Lord of the harvest has an instrument in His hand, which sets up a current of air, and the wheat falls in one heap, while the husks are blown farther, and lie at the edge of the floor. Mark the majestic emphasis on the Christ's ownership in the two phrases, '_His_ floor' and '_His_ garner.' Notice, too, the fact which determines whether a man is chaff or wheat--namely, his yielding to or rejecting the fiery baptism which Christ offers. Ponder that awful emblem of an empty, rootless, fruitless, worthless life, which John caught up from Psalm I. Thankfully think of the care and safe keeping and calm repose shadowed in that picture of the wheat stored in the garner after the separating act. And let us lay on awed hearts the terrible doom of the chaff. There are two fires, to one or other of which we must be delivered. Either we shall gladly accept the purging fire of the Spirit which burns sin out of us, or we shall have to meet the punitive fire which burns up us and our sins together. To be cleansed by the one or to be consumed by the other is the choice before each of us. II. Verses 18-20 show John as the preacher and martyr of righteousness. Luke tells his fate out of its proper place, in order to finish with him, and, as it were, clear the stage for Jesus. Similarly the Baptist's desert life is told by anticipation in chapter i. 80. That treatment of his story marks his subordination. His martyrdom is not narrated by Luke, though he knew of it (Luke ix. 7-9), and this brief summary is all that is said of his heroic vehemence of rebuke to sin in high places, and of his suffering for righteousness' sake. John's message had two sides to it, as every gospel of God's has. To the people he spoke good tidings and exhortations; to lordly sinners he pealed out stern rebukes.