Bible passage: 1 Thessalonians 5:1-9
Written: About 50 AD
In a letter addressed to the church of the Thessalonians, we are reminded that the return of Jesus, which is referenced here as the "day of the Lord," will take people by surprise.
In fact, we are told that the day will come "like a thief in the night" (1 Thessalonians 5:2), during a time when people are talking about peace and safety (1 Thessalonians 5:3).
The letter, which is part of the New Testament, was sent by Paul, Silas (Silvanus), and Timothy to Christians in Thessalonica, which is in Greece. It serves to reinforce the idea among Christians to always be prepared for Judgment Day because it can take place at any time.
It serves also as a warning to non-believers:
"The appearance of the Lord will be announced in a flash and a twinkling of an eye by the voice of the archangel and a trumpet's blast. Once this has begun there can be no preparations by unbelievers in order to escape their ruin in God's judgment. It will be too late." - David P. Kuske, Thessalonians, The People's Bible (Milwaukee, WI: Northwestern Pub. House, 1984), 51.
Here is 1 Thessalonians 5:1-9 (WEB):
1 But concerning the times and the seasons, brothers, you have no need that anything be written to you. 2 For you yourselves know well that the day of the Lord comes like a thief in the night. 3 For when they are saying, "Peace and safety," then sudden destruction will come on them, like birth pains on a pregnant woman. Then they will in no way escape. 4 But you, brothers, aren't in darkness, that the day should overtake you like a thief. 5 You are all children of light and children of the day. We don't belong to the night, nor to darkness, 6 so then let's not sleep, as the rest do, but let's watch and be sober. 7 For those who sleep, sleep in the night; and those who are drunk are drunk in the night. 8 But since we belong to the day, let's be sober, putting on the breastplate of faith and love, and for a helmet, the hope of salvation. 9 For God didn't appoint us to wrath, but to the obtaining of salvation through our Lord Jesus Christ,