Continuing the metaphor of the day of the Lord—Christ’s return—coming unexpectedly like a thief in the night (1 Thess. 5:1–3), Paul in today’s passage uses the imagery of darkness and light to explain how we are to live while waiting for Jesus to come back. This shift of metaphors makes sense, for thieves often work at night and not during the day when they might be seen.
Having warned that unbelievers will not be prepared for the sudden coming of the Lord (v. 3), Paul says that believers will not be caught off guard because we are not “in darkness” and we are not “of the night or of the darkness” (vv. 4–5). We should not sleep as others do (vv. 6–7). The notion of being unprepared for Christ’s return is stressed here. When people are asleep, they are unconscious and not truly ready for unexpected visitors. Those who are not prepared for Jesus’ sudden return are like those who sleep or who are in darkness. Christians, however, are “children of light, children of the day” (v. 5). Both Jesus and Paul elsewhere use this metaphor to refer to the reality of Christians’ being in Christ, who is the true light from God (John 12:35–36; Eph. 5:8). Because believers are united to Christ and have been saved from sin, we are prepared for the day of the Lord. We do not know precisely when it will occur, but we know that we will be rescued and not destroyed on that day.
Yet, although we are children of the light and prepared for the Lord who will come as a thief in the night, we must still prepare ourselves for the Lord’s coming. We are prepared, but we have to prepare ourselves further. Here the Apostle emphasizes an expectant waiting for the Lord, an active waiting. In his commentary on 1 and 2 Thessalonians, Gregory Beale draws an analogy with our own experience of waiting for thieves. Knowing that a thief may come, we lock our doors and install alarms, but we do not stay home all the time until he comes. Instead, we go on with our lives, readying ourselves and our homes without being paralyzed.
We prepare ourselves for Christ’s return in like manner. The Apostle tells us not to stop everything and wait for Jesus to come back but to be active, to live lives of sobriety, that is, lives of self-control. We are to pursue holiness, putting on the armor of faith, hope, and love (1 Thess. 5:6–8). Paul wants us to grow into the fullness of God’s image, reflecting the divine character in our thoughts and actions.