What does Matthew 24:42 mean?

Jesus now arrives at His main point about His return as judge and king (Matthew 24:3). It will come unexpectedly, as the flood did in Noah's day (Genesis 6:5–8). Before being swept away, the people then were just going about their daily lives as if nothing would ever change. Then they were gone (Matthew 24:37–39). In that same way, Christ's return will be unexpected. The signs will be clear (Matthew 24:27–31), but only when they occur, at which point it will be too late to react.

Pointedly, Christ made it clear that no person can claim to know the time of His return (Matthew 24:36). Absolutely every prediction that gives a date of the second coming is based on false premises.

That leaves only one option for those who want to be ready: His followers must "stay awake" all the time. Of course, Jesus is not speaking literally, suggesting one should avoid actual sleep. Instead, He is telling them to live in a state of awareness. Believers should never lapse into the false notion that what happens in this life, from day to day, is all that will ever happen (2 Peter 3:3–7; James 4:13–14). Wakeful believers remember that this life is temporary, and the next life is eternal. The next life can begin without warning.

Far too many people live only for today or for the days before this life ends. They put off dealing with the reality of God's judgment and eternity as if they are sleeping through the alarm. The opportunity to trust in Christ for salvation is limited to the length of one's life before death (Hebrews 9:27) or the return of Christ (Revelation 19:11–15). In either case, the time is short. By the time a person knows their moment has come, their choice has already been made.