Now concerning the times and the seasons, brothers,[a] you have no need to have anything written to you. For you, yourselves are fully aware that the day of the Lord will come like a thief in the night. While people are saying, “There is peace and security” then sudden destruction will come upon them as labor pains come upon a pregnant woman, and they will not escape. But you are not in darkness, brothers, for that day to surprise you like a thief. For you are all children of light, children of the day. We are not of the night or of the darkness. So then let us not sleep, as others do, but let us keep awake and be sober. For those who sleep, sleep at night, and those who get drunk, are drunk at night. But since we belong to the day, let us be sober, having put on the breastplate of faith and love, and for a helmet the hope of salvation. For God has not destined us for wrath, but to obtain salvation through our Lord Jesus Christ, who died for us so that whether we are awake or asleep we might live with him. Therefore encourage one another and build one another up, just as you are doing.
The “day of the Lord” is the day of reward and judgment at His coming. It is his day of vengeance. When he comes in his glory with the holy angels, he will sit upon his throne and separate the nations who have been gathered to him as a shepherd divides the sheep from the goats (cf. Matth. 25:31-32, 2 Thes. 1:7-9). It is a day of judgment for the unjust (2 Peter 3:7).
Matthew 24:30 tells us that he will come in the clouds of heaven with power and great glory and all the tribes of the earth will mourn.
The time of his coming was imminent or soon. Coming as a thief correlates with the view of no one knowing the day or the hour (cf. Mark 13:32, Luke 12:40). Jesus, however, gives his disciples signs of his coming and reminds them that all these things will happen in that generation (Mat. 24:34). His coming is compared to the destruction of the earth by water when the people were eating and drinking and given to marriage. Yet, in both cases, enough information and signs were given to know that destruction was soon approaching.
Paul explains that, as “children of light” or of the day, that day will not overtake them as a thief. They have put on the breastplate of faith and love, and for a helmet the hope of salvation. They are watching for him and, unlike the foolish virgins (cf. Matthew 25), they are prepared. Whether they live or die, they will live with Christ because the dead will be raised and those who are alive and remain will be caught up with them. In either case, they will not be unprepared for death or for his coming.