The Deluge: (Unexpectedness of) Suddenness of Christ's Coming

No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father. …

Just as it was in the days of Noah, so also will it be in the days of the Son of Man:

People were eating and drinking, marrying and being given in marriage, up to the day Noah entered the ark. Then the flood came and destroyed them all. …