What does Matthew 24:38 mean?
The people in Noah's day (Genesis 6:5–8) were leading their normal lives, day after day. Everyone was doing what people do: eating, drinking, getting married, giving their children in marriage. They did not realize that absolute catastrophe was upon them until it was there. By the time they recognized what was happening, it was far too late. Jesus has just said that His second coming, the coming of the Son of Man (Matthew 24:29), will be similar in that way. "Normal life" will not be paused or extraordinary. Everyone will just be going about their business as if life will go on as normal forever.Those who were living on earth moments before the flood learned the hard way that God's judgment could bring normal lives to a quick and unexpected end. The same will be true when Christ returns in judgment. He will interrupt a world full of people expecting the next day to unspool just as all the days before it did (2 Peter 3:3–7; James 4:13–14).
Jesus tells His followers not to make this mistake. Rather, they should live in readiness for His return.