"The day of the Lord" is a famous expression in the Old Testament; it runs through all prophecy, and is one of its most characteristic ideas. It means a day which belongs in a peculiar sense to God: a day which He has chosen for the perfect manifestation of Himself, for the thorough working out of His work among men. It is impossible to combine in one picture all the traits which prophets of different ages, from Amos downward, embody in their representations of this great day. It is heralded, as a rule, by terrific phenomena in nature: the sun is turned into darkness and the moon into blood, and the stars withdraw their light; we read of earthquake and tempest, of blood and fire and pillars of smoke. The great day ushers in the deliverance of God's people from all their enemies; and it is accompanied by a terrible sifting process, which separates the sinners and hypocrites among the holy people from those who are truly the Lord's. Wherever it appears, the day of the Lord has the character of finality. It is a supreme manifestation of judgment, in which the wicked perish for ever; it is a supreme manifestation of grace, in which a new and unchangeable life of blessedness is opened to the righteous. Sometimes it seemed near to the prophet, and sometimes far off; but near or far, it bounded his horizon; he saw nothing beyond. It was the end of one era, and the beginning of another which should have no end. This great conception is carried over by the Apostle from the Old Testament to the New. The day of the Lord is identified with the Return of Christ. All the contents of that old conception are carried over along with it. Christ's return bounds the Apostle's horizon; it is the final revelation of the mercy and judgment of God. There is sudden destruction in it for some, a darkness in which there is no light at all; and for others, eternal salvation, a light in which there is no darkness at all. It is the end of the present order of things, and the beginning of a new and eternal order. All this the Thessalonians knew; they had been carefully taught it by the Apostle. He did not need to write such elementary truths, nor did he need to say anything about the times and seasons[18] which the Father had kept in His own power. They knew perfectly all that had been revealed on this matter, viz., that the day of the Lord comes exactly as a thief in the night. Suddenly, unexpectedly, giving a shock of alarm and terror to those whom it finds unprepared,--in such wise it breaks upon the world. The telling image, so frequent with the Apostles, was derived from the Master Himself; we can imagine the solemnity with which Christ said, "Behold, I come as a thief. Blessed is he that watcheth and keepeth his garments, lest he walk naked, and they see his shame."[19] The New Testament tells us everywhere that men will be taken at unawares by the final revelation of Christ as Judge and Saviour; and in so doing, it enforces with all possible earnestness