1Thessalonians 5:4-5 But you, brethren, are not in darkness, that that day should overtake you as a thief. You are all the children of light, and the children of the day: we are not of the night, nor of darkness.
‘Are not in darkness, that that day should overtake you as a thief.’ Christians are not in ignorance and darkness about the day of the Lord (5:1-2, 4-5, 9). The rapture takes place at least seven years before the second coming (2Thess. 2:7). Therefore, they will not be here for that day to overtake them as a thief like it will the ungodly (5:2-5). The Jews had a tradition that God would judge the Gentiles at night when they were careless and asleep in sin, but would judge the Jews in the day when they would be keeping the law. But both Jews and Gentiles who miss the rapture will have the day of the Lord come upon them as a thief. It is only brethren who will be translated and escape this day (5:4-5, 9; Luke 21:36).
‘You are all the children of light, and the children of the day: we are not of the night, nor of darkness.’ We are all Christians and will escape that sudden destruction (5:4-5, 9). Since we are of light and of the day, not of the darkness and night, we will not suffer the destruction appointed to children of darkness. The reason is clear from this fact, as well as what is stated in 1Thessalonians 5:9 and 2Thessalonians 2:7.