Mark 13:15

The one on the roof ¹  must not come down or go inside to take anything out of his house. ² 

Ge 19:15-17,22,26; Job 2:4; Pr 6:4,5; Pr 22:3; Mt 24:16-18; Lu 17:31-33; Ac 27:18,19,38; Php 3:7,8; Heb 11:7

¹ sn Most of the roofs in the NT were flat roofs made of pounded dirt, sometimes mixed with lime or stones, supported by heavy wooden beams. They generally had an easy means of access, either a sturdy wooden ladder or stone stairway, sometimes on the outside of the house.

² sn The nature of the judgment coming upon them will be so quick and devastating that one will not have time to come down or go inside to take anything out of his house. It is best just to escape as quickly as possible.