“But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for an helmet, the hope of salvation.” 1 Thes. 5:8.
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, 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.
Having put on the breastplate. He adds this, that he may the more effectually shake us out of our stupidity, for he calls us as it were to arms, that he may shew that it is not a time to sleep. It is true that he does not make use of the term war; but when he arms us with a breastplate and a helmet, he admonishes us that we must maintain a warfare. Whoever, therefore, is afraid of being surprised by the enemy, must keep awake, that he may be constantly on watch. As, therefore, he has exhorted to vigilance, on the ground that the doctrine of the gospel is like the light of day, so he now stirs us up by another argument — that we must wage war with our enemy. From this it follows, that idleness is too hazardous a thing. For we see that soldiers, though in other situations they may be intemperate, do nevertheless, when the enemy is near, from fear of destruction, refrain from gluttony and all bodily delights, and are diligently on watch so as to be upon their guard. As, therefore, Satan is on the alert against us, and tries a thousand schemes, we ought at least to be not less diligent and watchful.