Luke 17:31
In that day, he which shall be upon the housetop, and his stuff in the house, let him not come down to take it away: and he that is in the field, let him likewise not return back. In that day, he which shall be upon the housetop, and his stuff in the house, let him not come down to take it away: and he that is in the field, let him likewise not return back.
Jesus' warning about the day of the Lord is illustrated by the days of Noah and Lot, when judgment fell suddenly and left no opportunity to prepare after it began. That day must not catch anyone unready, and no one may turn back then to secure earthly possessions. Watchfulness and prayer are required now, with walking in Jesus' footsteps while working out salvation with fear and trembling.
When that day comes there is no time to return for what was left behind, so the one on the housetop with goods in the house must not come down to take them away. Likewise the one in the field must not turn back, but must leave immediately without retrieving possessions. This urgency applies to the flight from cities and villages in the time of trouble, when the wicked pursue the saints and escape must be without delay. The day of the Lord will come as a thief in the night to all who are not watching and praying and also working, which lays great necessity on those who have the light in this time of peril to walk in Jesus' footsteps and work out their own salvation with fear and trembling.