“not go down.” How could a person on the roof leave town without coming down from the roof? It was often possible to get quite close to the edge of town without going down into a house. In the biblical times, houses had flat roofs, and the Mosaic Law commanded that a railing be built around the roof so people would not fall off (Deut. 22:8). People would spend time on the roof when the weather was nice, which is why Peter went up on the rooftop to pray (Acts 10:9).
The houses were built close together, often even having common walls, and were generally close enough to get from one roof to another. The streets between the houses were usually very narrow. That meant that getting to the outside of town by traveling rooftop to rooftop was usually quicker than using the narrow streets through town. Moving roof to roof was known as “the road of the roofs,” and that was why Jesus said that when people saw the signs of the end times they should flee town without going back down into their houses (Matt. 24:17; Mark 13:15; Luke 17:31). In contrast to the flat roofs, the narrow and often winding roads between the houses were not a good way to travel quickly through town because they would clog up so quickly. [For more on houses, see commentaries on Isaiah 22:1 and Proverbs 17:19].