Charles Ellicott Commentary Matthew 24:17

"let him that is on the housetop not go down to take out things that are in his house:" — Matthew 24:17 (ASV)

Let him which is on the housetop — The houses in the streets of Jerusalem were built in a continuous line and with flat roofs, so that a person could pass from house to house without going down into the street until they reached a point near the city wall or gate to make their escape. At a moment of danger, such as the one arising from the factions within the city rather than the invaders outside, any delay could prove fatal. People were to escape as though their life were given them for a prey (Jeremiah 45:5), without thinking of their goods or possessions.