1 Thessalonians 5:4-8

Verse 4

But ye, brethren, are not in darkness - Probably St. Paul refers to a notion that was very prevalent among the Jews, viz.: that God would judge the Gentiles in the night time, when utterly secure and careless; but he would judge the Jews in the day time, when employed in reading and performing the words of the law. The words in Midrash Tehillim, on Psa 9:8, are the following: When the holy blessed God shall judge the Gentiles, it shall be in the night season, in which they shall be asleep in their transgressions; but when he shall judge the Israelites, it shall be in the day time, when they are occupied in the study of the law. This maxim the apostle appears to have in view in the 4th, 5th, 6th, 7th, and 8th verses. (1Thes 5:4-8)
Verse 5

Ye are all the children of light - Ye are children of God, and enjoy both his light and life. Ye are Christians - ye belong to him who has brought life and immortality to light by his Gospel. This dispensation, under which ye are, has illustrated all the preceding dispensations; in its light all is become luminous; and ye, who walked formerly in heathen ignorance, or in the darkness of Jewish prejudices, are now light in the Lord, because ye have believed in him who is the light to lighten the Gentiles, and the glory and splendor of his people Israel.

We are not of the night, nor of darkness - Our actions are such as we are not afraid to expose to the fullest and clearest light. Sinners hate the light; they are enemies to knowledge; they love darkness; they will not receive instructions; and their deeds are such as cannot bear the light.
Verse 6

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.
Verse 7

For they that sleep - Sleepers and drunkards seek the night season; so the careless and the profligate persons indulge their evil propensities, and avoid all means of instruction; they prefer their ignorance to the word of God's grace, and to the light of life. There seems to be here an allusion to the opinion mentioned under 1Thes 5:4 (note), to which the reader is requested to refer. It may be remarked, also, that it was accounted doubly scandalous, even among the heathen, to be drunk in the day time. They who were drunken were drunken in the night.
Verse 8

Putting on the breastplate - We are not only called to Work, but we are called also to fight; and that we may not be surprised, we must watch; and that we may be in a condition to defend ourselves, we must be sober; and that we may be enabled to conquer, we must be armed: and what the breastplate and helmet are to a soldier's heart and head, such are faith, love, and hope to us. Faith enables us to endure, as seeing him who is invisible; love excites us to diligence and activity, and makes us bear our troubles and difficulties pleasantly; hope helps us to anticipate the great end, the glory that shall be revealed, and which we know we shall in due time obtain, if we faint not. For an explanation of the different parts of the Grecian armor, as illustrating that of the Christian, see the notes on Ephesians 6 (note), where the subject is largely explained.
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