1-3 Now, brothers and sisters, about times and dates we do not need to write to you, for you know very well that the day of the Lord will come like a thief in the night.  While people are saying, ‘Peace and safety’, destruction will come on them suddenly, as labour pains on a pregnant woman, and they will not escape. 4-5 But you, brothers and sisters, are not in darkness so that this day should surprise you like a thief. You are all children of the light and children of the day. We do not belong to the night or to the darkness. 

6-8 So then, let us not be like others, who are asleep, but let us be awake and sober. For those who sleep, sleep at night, and those who get drunk, get drunk at night. But since we belong to the day, let us be sober, putting on faith and love as a breastplate, and the hope of salvation as a helmet.  9-11 For God did not appoint us to suffer wrath but to receive salvation through our Lord Jesus Christ. He died for us so that, whether we are awake or asleep, we may live together with him. Therefore encourage one another and build each other up, just as in fact you are doing. 1 Thessalonians 5:1-11 New International Version

If you woke up one morning to find that thieves had got into your house and, without disturbing your sleep, had taken away many goods, what would be your biggest reaction? Some might say they were amazed at how quiet the thieves must have been; most of us would say it was the total surprise and unexpectedness of what happened. If only we had got wind of the fact that someone was planning to rob us we would've been prepared for them. That's the illustration Paul used to urge Christians to whom he was writing to not be 'caught out' by the return of Jesus Christ to planet earth.

In the preceding verses he had assured them that Christians who had 'fallen asleep' (i.e died) would return with Christ and their bodies would be raised, while the bodies of Christians who are still alive when Jesus returns will be transformed in an instant to be with God forever. But this wonderful truth has important implications for how we live in this world. How will people who care nothing for Christ be living when Christ returns? (vs 1-3 & 6-8)

They'll be living as if there's nothing to worry about, no repercussions for the lifestyle they live, no judgement to face, and no hell to fear. He likens them to people living in the dark – either fast asleep, or getting drunk with their buddies. For them the sudden reappearance of Jesus Christ will be a complete surprise; something they were not expecting and for which they’d made no preparation. The book called Revelation says that day will be a day “when the kings of the earth, the nobles, the generals, the rich, the powerful, and every slave and free person hid in the caves and among the rocks of the mountains. And they said to the mountains and to the rocks, 'Fall on us and hide us from the face of the one seated on the throne and from the wrath of the Lamb' - because the great day of their wrath has come! And who is able to stand?” Revelation 6:15-17. What’s the big difference between these people and true Christians? (vs 4-5)

While Christians don't know the exact year or day when Jesus will return, they know for certain that He WILL return! They are living in the light that the gospel message has brought into their lives. And because they know these things, what does Paul urge them to put on, and what 'parts of the body' does that suggest we need to guard? (vs 6-8)

Faith and love are the breastplate that will will shield the affections of our heart from being misplaced, and from being destroyed by the wickedness of sin. And the wonderful hope the gospel has brought of being saved from God's wrath will be the helmet that shields our heads and our thinking from being deceived by the false peace and safety that sinners think they have. Paul urges Christians to remind one another of these things to encourage ourselves to keep living in the light God has given us, so that we won't be 'caught out' by the return of Christ and the day of judgement.