Text: 1 Thessalonians 5:1-11
For you yourselves are fully aware that the day of the Lord will come like a thief in the night (v. 2).
An Unexpected Thief
One day when I was about ten years old, my grandparents traveled from Vermont to New Brunswick to visit us. They were going to arrive late at night, so my dad decided to leave the garage door open for them. The next day I discovered that my bike was gone. Apparently a thief in the night and walked through the open garage door and stolen my bike.
In order for a thief to be successful at robbing a house, his arrival has to be unexpected. Jesus declared that when he returns to earth, he will come like a thief in the night:
“Stay awake, for you do not now on what day your Lord is coming. But know this, that if the master of the house had known in what part of the night the thief was coming, he would have stayed awake and would not have let his house be broken into. Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect” (Matt. 24:42-44; cf. 2 Peter 3:10; Rev. 16:15).When Jesus returns, most of the world will not be expecting him. He will come “like a thief in the night” (v. 2).
Could Today Be the Day?
The apostle Paul writes, “But concerning that day and hour [i.e., the day and hour when Jesus will return] no one knows, not even the angels of heaven, nor the Son, but the Father only” (v. 1). Jesus himself said, “Concerning that day or that hour, no one knows” (Mark 13:32). None of us knows when Jesus will return. If someone gives a date for the return of Jesus, ignore that person. He or she doesn’t know when it will happen.
The apostle Peter also writes that the coming of Jesus will be “like a thief in the night” (2 Peter 3:10). He states that “scoffers will come in the last days scoffing.” They will ask, “Where is the promise of his coming?” (2 Peter 3:3-4). The promise was given 2,000 years ago, but Peter goes on to say, “Do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day” (2 Peter 3:8). So why has Jesus returned yet? Here’s Peter’s answer: “The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance” (2 Peter 3:9).
Could Jesus return today? Maybe. It’s possible. No one knows whether Jesus will return today, tomorrow, or a thousand years from now. But we should live each day thinking that today could be the day of the Lord’s return.
The Day of the Lord
What is “the day of the Lord” (v. 2)? The day of the Lord is “that eschatological event when the Lord comes to judge the inhabitants of the earth and to pour out his wrath because of sin.”  “Blow a trumpet in Zion; sound an alarm on my holy mountain! Let all the inhabitants of the land tremble, for the day of the LORD is coming; it is near” (Joel 2:1).
For those not expecting the return of Jesus, the day of the Lord will “come like a thief in the night” (v. 2). It will be an unwelcome surprise. “While people are saying, ‘There is peace and safety,’  then sudden destruction will come upon them as labor pains come upon a pregnant woman, and they will not escape” (v. 3).
For the Christian, the day of the Lord is not a day to be feared. “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” (vv. 9-10). For the Christians, the day of the Lord is a day of salvation, not a day of judgment. Paul ends this section by writing, “Therefore encourage one another and build one another up, just as you are doing” (v. 11).
Paul writes, “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” (vv. 4-6). To “sleep” is to live without expecting the Lord’s return.
One of the Christian’s greatest enemies is complacency. If you examine Paul’s letters, you’ll discover that he never promotes complacent Christianity. He always encourages his readers to keep on progressing, to keep on striving to become more like Jesus.
Paul goes on to day, “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” (v. 8). This is an allusion to Isaiah 59:17: “He put on righteousness as a breastplate and a helmet of salvation on his head.” The image is one of Jesus coming as a warrior.
As we wait for the Lord’s return, we are to put on “the breastplate of faith and love and “a helmet the hope of salvation.” Faith, love, and hope are the three great Christian virtues: “remembering before our God and Father your work of faith and labor of love and steadfastness of hope in our Lord Jesus Christ” (1:3)
Our first concern should not be when Jesus will return but how we should live until he returns. If we lived each day as though it could be the day of the Lord’s return, we would overcome our complacency.
 G. L. Green, The Letters to the Thessalonians, 232.
 Green comments, “With the establishment of the pax Romana under Augustus, peace and safety became the byword in the city as throughout the empire, and so the apocalyptic teaching of the apostles would have sounded decidedly strange” (233).