5 Now concerning the times and the seasons, brothers,^[a] you have no need to have anything written to you. ² For you yourselves are fully aware that the day of the Lord will come like a thief in the night. ³ 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. ⁴ But you are not in darkness, brothers, for that day to surprise you like a thief. ⁵ For you are all children^[b] of light, children of the day. We are not of the night or of the darkness. ⁶ So then let us not sleep, as others do, but let us keep awake and be sober. ⁷ For those who sleep, sleep at night, and those who get drunk, are drunk at night. ⁸ 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. ⁹ For God has not destined us for wrath, but to obtain salvation through our Lord Jesus Christ, ¹⁰ who died for us so that whether we are awake or asleep we might live with him. ¹¹ Therefore encourage one another and build one another up, just as you are doing.

— 1 Thessalonians 5:1-11

And here is a sermon from Pastor John Macarthur to expand upon it and put it into context: