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.
The flood "took ... away" unsuspecting unbelievers. At the end, when Jesus returns to cut short the tribulation afflicting His own, few will see it coming. Like a tsunami, the wave of glory will wipe out those not anchored in faith and connection to Jesus. Those left standing, those "left behind", will be looking up in newfound peace and rapturous wonder.
The message: hang on, love until He pulls you up or clears all the debris around you.
