Ye are all the children of light, and the children of the day: we are not of the night, nor of darkness…let us watch and be sober.
1 THESSALONIANS 5:5, 6
We of the Christian faith need not go on the defensive, for it is the modern man of the world who is the dreamer, not the Christian believer!
The sinner can never be quite himself. All his life he must pretend. He must act as if he were never going to die, and yet he knows too well that he is. He must act as if he had not sinned, when in his deep heart he knows very well that he has. He must act unconcerned about God and judgment and the future life, and all the time his heart is deeply disturbed about his precarious condition. He must keep up a front of nonchalance while shrinking from facts and wincing under the lash of conscience. All his adult life he must dodge and hide and conceal. When he finally drops the act he either loses his mind or tries suicide.
If realism is the recognition of things as they actually are, the Christian is of all persons the most realistic. He of all intelligent thinkers is the one most concerned with reality. He pares things down to their stark essentials and squeezes out of his mind everything that inflates his thinking. He demands to know the whole truth about God, sin, life, death, moral accountability and the world to come. He wants to know the worst about himself in order that he may do something about it. He takes into account the undeniable fact that he has sinned. He recognizes the shortness of time and the certainty of death. These he does not try to avoid or alter to his own liking. They are facts and he faces them full on.
The believer is a realist—his expectations are valid and his faith well grounded!
Far from being in the darkness, believers are all sons of light and sons of day (cf. Luke 16:8; John 12:36; Eph. 5:8). The phrase sons of is often part of an idiomatic Hebrew expression describing the dominant influence in a person’s life. The Old Testament uses the phrase “sons of Belial” (Judg. 19:22; 1 Sam. 2:12; 2 Sam. 23:6; 1 Kings 21:10 kjv) to describe worthless men who are by nature children of the devil (cf. 2 Cor. 6:15). Jesus nicknamed James and John “Sons of Thunder” (Mark 3:17) because of their volatile, aggressive personalities. Barnabas’s name literally means “Son of Encouragement” (Acts 4:36), denoting his gentle, encouraging nature. Thus, to describe believers as sons of light is to say that light is the dominant influence in their lives. Adding the parallel phrase sons of day reinforces Paul’s point; light belongs to day just as darkness belongs to night.
To drive home his point, Paul declared emphatically, We are not of night nor of darkness. Believers live in an entirely different sphere than those who will experience God’s wrath in the Day of the Lord. As sons of light and sons of day, believers “walk in newness of life” (Rom. 6:4), are new creatures in Christ (2 Cor. 5:17), are new creations (Gal. 6:15), are “seated … in the heavenly places in Christ Jesus” (Eph. 2:6), and have their lives “hidden with Christ in God” (Col. 3:3). Therefore, the Thessalonians did not need to fear missing the Rapture, being caught in the Day of the Lord, or experiencing God’s wrath and condemnation. Believers live in a separate sphere of life, where judgment cannot come.
The phrase so then emphasizes the inseparable link between Christians’ nature and their behavior, between their character and their conduct—a truth taught throughout the New Testament (cf. 2:12; 4:1; Eph. 4:1, 17; Phil. 1:27; Col. 1:10). What people are determines how they act; believers are day people and must act accordingly.
On that basis, Paul exhorted the Thessalonians, let us not sleep as others do, but let us be alert and sober. The apostle did not need to exhort them to be day people, because their nature was permanently fixed by the transforming, regenerating power of God in salvation. But because that new nature is incarcerated in fallen, sinful human flesh (cf. Rom. 7:14–25), it is possible for day people to do deeds of the darkness. Therefore, Paul exhorted the Thessalonians to live consistently with their new natures. The present tense verbs indicate that the Thessalonians were to be continuously awake, alert, and sober. Rather than threaten them with chastening, the apostle appealed to their sense of spiritual dignity. As children of the day and the light, it was unthinkable for them to participate in the deeds of darkness (cf. Eph. 4:1; 5:11).
5 Paul’s assertion that believers are “all sons of the light and sons of the day” rules out living in darkness. “All” brings reassurance that no one is excluded. The fainthearted may take heart, as may others who have been confused about the parousia (cf. 4:11–12; 5:14; Frame, 184). “The day” here does not refer to the eschatological day of the Lord, as the anarthrous (i.e., lacking a definite article) construction attests, but is used metaphorically in association with spiritual light (cf. Lightfoot, 73). Verse 5 guarantees the readers’ participation in a spiritual environment entirely different from that of non-Christians.
To reinforce his point, Paul returns to the negative side. Putting light and day in inverse order, he excludes himself, along with all Christians, from the night of moral insensitivity. By a casual change from “you” to “we,” he takes his place with his readers in accepting the exhortation of v. 6. This dulls the edge of what would otherwise be a sharp rebuke (cf. Frame, 185).
6 This verse provides a solid basis (“so then,” ara oun) for the ethical behavior Paul now urges on his readers—a lifestyle free from moral laxity. Mē katheudōmen (lit., “let us not sleep,” GK 2761) represents the ethical insensitivity that besets people in the other realm (“like others”; cf. 4:13). Though it is impossible for the day of the Lord to catch Christians unprepared, it is possible for them to adopt the same lifestyle as those who will be caught unawares. Paul urges his readers not to let this happen.
Conduct in keeping with “the light” and “the day” also includes alertness. Inattention to spiritual priorities is utterly inappropriate for those who will not be subject to the coming day of wrath. Though the Thessalonians were, if anything, overly watchful to the point of neglecting other Christian responsibilities (4:11–12; 2 Th 3:6–15), they were not to cease watching altogether.
Apparently self-control was a great need. Nēphō (“to be self-controlled, be sober,” GK 3768) is found with grēgoreō (“to be alert, watch,” GK 1213) in the noneschatological context of 1 Peter 5:8. Its usage in 1 Peter 1:13 and 4:7 is eschatological. Nēphō denotes sobriety. To counteract what might become a state of wild alarm or panic, Paul urges self-control as a balance for vagaries arising from distorted views of the parousia. Undue eschatological excitement was a serious malady; spiritual sobriety was the cure.
5:5 For. Paul grounds his assurance of v. 4 in the Thessalonians’ status and destiny. children of light. This phrase is used in Jewish literature and in the NT (e.g., Luke 16:8; John 12:36) of those who belong to the realm of God and his salvation (Col. 1:13). children of the day. This phrase, which is unique to Paul, seems to link the concepts of “light” and “day” together. Thus, because Jesus is “the light of the world” (John 8:12; 9:5), Christians are “children of the light”; but Christians are also those who are called to live a godly life as people who “belong to the day” (1 Thess. 5:8) and who are destined to inherit salvation on “the day of the Lord,” when Christ (the light of the world) will return in power and great glory (cf. Matt. 24:30; Mark 13:26; Luke 21:27). We. Paul shifts to the first person plural to reinforce his confirmation and perhaps to prepare for and soften the exhortation of 1 Thess. 5:6–8. night … darkness. The dominion of evil and enmity with God.
5:6 So then. Paul gives general exhortations based on the reassurances of v. 5. To sleep is to be morally and spiritually disengaged, and/or living without a consciousness of the coming day.
5:5 children of light The Greek phrase used here, huioi phōtos, refers to people characterized by light. In this context, light symbolizes God’s favor toward those who will be spared from His judgment. In the ot, light symbolizes God’s favor (Prov 4:18; Psa 112:4) and truth (Psa 119:130).
darkness See note 1 Thess 5:4.
5:6 let us not sleep Earlier in this letter, Paul used a Greek word for “sleep,” koimaō, metaphorically to describe those who have died (4:13). In this verse, he uses a different Greek word, katheudō, also translated “sleep,” to refer to being unaware of God, His workings, and His return.
 Tozer, A. W., & Smith, G. B. (2015). Evenings with tozer: daily devotional readings. Chicago, IL: Moody Publishers.
 MacArthur, J. F., Jr. (2002). 1 & 2 Thessalonians (p. 158). Chicago: Moody Press.
 MacArthur, J. F., Jr. (2002). 1 & 2 Thessalonians (p. 159). Chicago: Moody Press.
 Thomas, R. L. (2006). 1 Thessalonians. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Ephesians–Philemon (Revised Edition) (Vol. 12, p. 424). Grand Rapids, MI: Zondervan.
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 Barry, J. D., Mangum, D., Brown, D. R., Heiser, M. S., Custis, M., Ritzema, E., … Bomar, D. (2012, 2016). Faithlife Study Bible (1 Th 5:5–6). Bellingham, WA: Lexham Press.