As Paul and other biblical writers explain it, the result of Christ’s unforeseen coming will be sudden destruction on those who are unprepared:
While people are saying, There is peace and security, then sudden destruction will come upon them as labour pains come upon a pregnant woman, and they will not escape(1 Thessalonians 5:3). Now again, Paul is mirroring the earlier teaching of the Lord Jesus. Jesus compared the world on the brink of his return to the ancient world, unprepared on the brink of Noah’s flood:For as were the days of Noah, so will be the coming of the Son of Man. For as in those days before the flood they were eating and drinking, marrying and giving in marriage, until the day when Noah entered the ark. And they were unaware until the flood came and swept them all away—so will be the coming of the Son of Man(Matthew 24:37–39).Now, Jesus is not teaching that it is wrong to eat and drink—and there is nothing wrong with marrying or giving in marriage—but his point is that the world will be oblivious to the demands of God and to the looming threat of danger against all the rebels against God’s rule, for the simple reason that the world cares only about itself—its own worldly concerns, its pleasures, its ambitions, its worldly pursuits. Does that describe you? If so, see the peril in which you are living. It is the same thing that keeps people from thinking about Christ today. It is the devil’s best tactic. You think of C. S. Lewis and his clever, very insightful book, The Screwtape Letters. One of the pieces of advice the senior devil gave to the junior devil was if possible, not to say anything about spiritual things at all. Dope them with materialistic things, with sensuality, with pleasures, with activity. That is how you keep people destined for hell. And so it is, in fact, the same attitude now—of worldliness and sensual preoccupation—that keeps people from wondering about their souls. On that day, it will leave them unprepared for the coming of the Son of Man. Having not thought about God and eternity now, having given no concern for the well-being of their souls, they will receive Jesus suddenly, like a thief in the night—and it will be sudden destruction.1
Richard D. Phillips
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.