Therefore let us not sleep. He adds other metaphors closely allied to the preceding one. For as he lately shewed that it were by no means seemly that they should be blind in the midst of light, so he now admonishes that it were dishonorable and disgraceful to sleep or be drunk in the middle of the day. Now, as he gives the name of day to the doctrine of the gospel, by which the Christ, the Sun of righteousness (Malachi 4:2) is manifested to us, so when he speaks of sleep and drunkenness, he does not mean natural sleep, or drunkenness from wine, but stupor of mind, when, forgetting God and ourselves, we regardlessly indulge our vices. Let us not sleep, says he; that is, let us not, sunk in indolence, become senseless in the world. As others, that is, unbelievers, [1] from whom ignorance of God, like a dark night, takes away understanding and reason. But let us watch, that is, let us look to the Lord with an attentive mind. And be sober, that is, casting away the cares of the world, which weigh us down by their pressure, and throwing off base lusts, mount to heaven with freedom and alacrity. For this is spiritual sobriety, when we use this world so sparingly and temperately that we are not entangled with its allurements.

Footnotes

1 - "The refuse, as the word loipoi emphatically signifies, or the reprobate and worst of men.... The word katheudomen, signifies a deeper or a more intense sleep. It is the word that is used in the Septuagint to signify the sleep of death." (Daniel 12:2)--Howe's Works, (Lond. 1822,) vol. 6, p. 290. -- Ed

Therefore let us no sleep, as do others - As the wicked world does; compare notes, Matthew 25:5.
But let us watch - That is, for the coming of the Lord. Let us regard it as an event which is certainly to occur, and which may occur at any moment; notes, Matthew 25:13.
And be sober - The word here used (νήφω nēphō) is rendered sober in 1-Thessalonians 5:6, 1-Thessalonians 5:8; 1-Peter 1:13; 1-Peter 5:8; and watch in 2-Timothy 4:5, and 1-Peter 4:7. It does not elsewhere occur in the New Testament. It properly means, to be temperate or abstinent, especially in respect to wine. Joseph. Jewish Wars, 5. 5, 7; Xenophon, Cyr. 7. 5, 20; and then it is used in a more general sense, as meaning to be sober-minded, watchful, circumspect. In this passage there is an allusion to the fact that persons not only sleep in the night, but that they are frequently drunken in the night also. The idea is, that the Lord Jesus, when he comes, will find the wicked sunk not only in carnal security, but in sinful indulgences, and that those who are Christians ought not only to be awake and to watch as in the day-time, but to be temperate. They ought to be like persons engaged in the sober, honest, and appropriate employments of the day, and not like those who waste their days in sleep, and their nights in revelry.
A man who expects soon to see the Son of God coming to judgment, ought to be a sober man. No one would wish to be summoned from a scene of dissipation to his bar. And who would wish to be called there from the ball-room; from the theater; from the scene of brilliant worldly amusemet? The most frivolous votary of the world; the most accomplished and flattered and joyous patron of the ball-room; the most richly-dressed and admired daughter of vanity, would tremble at the thought of being summoned from those brilliant halls, where pleasure is now found, to the judgment bar. They would wish to have at least a little time that they might prepare for so solemn a scene. But if so, as this event may at any moment occur, why should they not be habitually sober-minded? Why should they not aim to be always in that state of mind which they know would be appropriate to meet him? Especially should Christians live with such vigilance and soberness as to be always prepared to meet the Son of God. What Christian can think it appropriate for him to go up to meet his Saviour from the theater, the ballroom, or the brilliant worldly party? A Christian ought always so to live that the coming of the Son of God in the clouds of heaven would not excite the least alarm.

Let us not sleep, as do others - Let us who are of the day - who believe the Gospel and belong to Christ, not give way to a careless, unconcerned state of mind, like to the Gentiles and sinners in general, who are stupefied and blinded by sin, so that they neither think nor feel; but live in time as if it were eternity; or rather, live as if there were no eternity, no future state of existence, rewards, or punishments.
Let us watch - Be always on the alert; and be sober, making a moderate use of all things.

Therefore let us not sleep as do others.... As the rest of the Gentiles, as unconverted persons, who are in a state of darkness, and are children of the night; let us not act that part they do, or be like them; which professors of religion too much are, when they indulge themselves in carnal lusts and pleasures, and are careless and thoughtless about the coming of the day of the Lord; and get into a stupid, drowsy, and slumbering frame of spirit; when grace lies dormant as if it was not, and they grow backward to, and slothful in the discharge of duty, and content themselves with the bare externals of religion; and become lukewarm and indifferent with respect to the truths and ordinance of the Gospel, the cause of God, the interest of religion, and glory of Christ; and are unconcerned about sins of omission or commission: and are willing to continue in such a position, being displeased at every admonition and exhortation given them to awake; but this is very unbecoming children of the light, and of the day:
but let us watch; over ourselves, our hearts, thoughts, affections, words and actions; and over others, our fellow Christians, that they give not into bad principles and evil practices; and against sin, and all appearance of it; against the temptations of Satan, the snares of the world, and the errors of wicked men, who lie in wait to deceive; and in the word and ordinances, and particularly in prayer, both unto it, in it, and after it; and for the second coming of Christ, with faith, affection, and patience; and the rather, because of the uncertainty of the time of it;
and be sober; not only in body, abstaining from excessive eating and drinking, using this world, and the good things of it, so as not to abuse them, or ourselves with them; but also in mind, that the heart be overcharged with the cares of this world; for men may be inebriated with the world, as well as with wine; and the one is as prejudicial to the soul as the other is to the body; for an immoderate care for, and pursuit after the world, chokes the word, makes it unfruitful, and runs persons into divers snares and temptations, and hurtful lusts. The Arabic version renders it, "let us repent"; and the Ethiopic version, "let us understand"; as intending the sobriety of the mind, repentance being an after thought of the mind, a serious reflection on past actions with sorrow and concern; and thinking soberly, and not more highly than a man ought to think of himself, his gifts, his attainments and abilities, in opposition to pride, vanity, and self-conceit, is very becoming; and shows a true and well informed understanding and judgment, and that a man is really sober and himself.

Most of mankind do not consider the things of another world at all, because they are asleep; or they do not consider them aright, because they sleep and dream. Our moderation as to all earthly things should be known to all men. Shall Christians, who have the light of the blessed gospel shining in their faces, be careless about their souls, and unmindful of another world? We need the spiritual armour, or the three Christian graces, faith, love, and hope. Faith; if we believe that the eye of God is always upon us, that there is another world to prepare for, we shall see reason to watch and be sober. True and fervent love to God, and the things of God, will keep us watchful and sober. If we have hope of salvation, let us take heed of any thing that would shake our trust in the Lord. We have ground on which to build unshaken hope, when we consider, that salvation is by our Lord Jesus Christ, who died for us, to atone for our sins and to ransom our souls. We should join in prayer and praise one with another. We should set a good example one before another, and this is the best means to answer the end of society. Thus we shall learn how to live to Him, with whom we hope to live for ever.

others--Greek, "the rest" of the world: the unconverted (1-Thessalonians 4:13). "Sleep" here is worldly apathy to spiritual things (Romans 13:11; Ephesians 5:14); in 1-Thessalonians 5:7, ordinary sleep; in 1-Thessalonians 5:10, death.
watch--for Christ's coming; literally, "be wakeful." The same Greek occurs in 1-Corinthians 15:34; 2-Timothy 2:26.
be sober--refraining from carnal indulgence, mental or sensual (1-Peter 5:8).

Awake, and keep awake - Being awakened, let us have all our spiritual senses about us.