36"No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father. 37As it was in the days of Noah, so it will be at the coming of the Son of Man. 38For in the days before the flood, people were eating and drinking, marrying and giving in marriage, up to the day Noah entered the ark; 39and they knew nothing about what would happen until the flood came and took them all away. That is how it will be at the coming of the Son of Man. 40Two men will be in the field; one will be taken and the other left. 41Two women will be grinding with a hand mill; one will be taken and the other left.
Those who believe in the Rapture see it clearly in verses 40 and 41. One is taken, the other is left. And given what is about to happen--the Great Tribulation--it's far, far better to be taken. The one who is left must suffer the curse of enduring seven horrible years of persecution and torture. It will, quite literally, be hell on earth. So those who are taken are taken up to Heaven for this time; rescued, as it were, from this great period of suffering.
But a careful reading of the text reveals that Jesus is saying quite the opposite. Being taken away is the worse fate, and it is much better for those who are left behind. The key to interpreting this passage is Jesus' retelling of the story of Noah.
"38For in the days before the flood, people were eating and drinking, marrying and giving in marriage, up to the day Noah entered the ark; 39and they knew nothing about what would happen until the flood came and took them all away." The flood waters, quite literally, took away, in judgment, all those wicked people. God exercised his judgment against humanity by taking away the overwhelming majority in the great flood, and leaving behind only a handful--Noah and his family. In the flood, it was far better to be left behind.
"That is how it will be at the coming of the Son of Man." As it was in the flood, so will it be at the return of Jesus. Those who are taken away are taken away in judgment. They are not transported to Heaven, rescued from the coming seven years of tribulation. No, they are taken away in the judgment of God. These are the goats that Jesus talks about just a chapter later, in Matthew 25:31-46.
The sheep, however, are left behind. Just like Noah and his family, those who are left are the ones who survived the judgment. They were not swept away by the flood waters. They remained. Better to be like Noah than like the mocking, arrogant heathen that died in the 'whelming flood.
Rather than giving an early teaching of the Rapture, Jesus is teaching that God's judgment at his return will come upon us unawares. We don't know when it's going to happen. But it will happen. And just like in the days of Noah, you will want to be left behind. Being taken away means that you are taken away in judgment. Those who are taken away are the goats, and those who are left behind are the sheep. Live in such a way that you will be left behind.