It may not be out of place to insist on the fact that "sober" in this passage means sober as opposed to drunk. No one would wish to be overtaken drunk by any great occasion; yet the day of the Lord is associated in at least three passages of Scripture with a warning against this gross sin. "Take heed to yourselves," the Master says, "lest haply your hearts be overcharged with surfeiting, and drunkenness, and cares of this life, and that day come on you suddenly as a snare." "The night is far spent," says the Apostle, "the day is at hand.... Let us walk honestly as in the day; not in revelling and drunkenness." And in this passage: "Let us, since we are of the day, be sober; they that be drunken are drunken in the night." The conscience of men is awakening to the sin of excess, but it has much to do before it comes to the New Testament standard. Does it not help us to see it in its true light when it is thus confronted with the day of the Lord? What horror could be more awful than to be overtaken in this state? What death is more terrible to contemplate than one which is not so very rare--death in drink?
Wakefulness and sobriety do not exhaust the demands made upon the Christian. He is also to be on his guard. "Put on the breastplate of faith and love; and for a helmet, the hope of salvation." While waiting for the Lord's coming, the Christian waits in a hostile world. He is exposed to assault from spiritual enemies who aim at nothing less than his life, and he needs to be protected against them. In the very beginning of this letter we came upon the three Christian graces; the Thessalonians were commended for their work of faith, labour of love, and patience of hope in the Lord Jesus Christ. There they were represented as active powers in the Christian life, each manifesting its presence by some appropriate work, or some notable fruit of character; here they constitute a defensive armour by which the Christian is shielded against any mortal assault. We cannot press the figure further than this. If we keep our faith in Jesus Christ, if we love one another, if our hearts are set with confident hope on that salvation which is to be brought to us at Christ's appearing, we need fear no evil; no foe can touch our life. It is remarkable, I think, that both here and in the famous passage in Ephesians, as well as in the original of both in Isaiah lix. 17, salvation, or, to be more precise, the hope of salvation, is made the helmet. The Apostle is very free in his comparisons; faith is now a shield, and now a breastplate; the breastplate in one passage is faith and love, and in another righteousness; but the helmet is always the same. Without hope, he would say to us, no man can hold up his head in the battle; and the Christian hope is always Christ's second coming. If He is not to come again, the very word hope may be blotted out of the New Testament. This assured grasp on the coming salvation--a salvation ready to be revealed in the last times--is what gives the spirit of victory to the Christian even in the darkest hour.
The mention of salvation brings the Apostle back to his principal subject. It is as if he wrote, "for a helmet the hope of salvation; salvation, I say; for God did not appoint us to wrath, but to the obtaining of salvation through our Lord Jesus Christ." The day of the Lord is indeed a day of wrath,--a day when men will cry to the mountains and to the rocks, Fall on us, and hide us from the face of Him that sitteth upon the throne, and from the wrath of the Lamb; for the great day of their wrath is come. The Apostle cannot remember it for any purpose without getting a glimpse of those terrors; but it is not for these he recalls it at this time. God did not appoint Christians to the wrath of that day, but to its salvation,--a salvation the hope of which is to cover their heads in the day of battle.