Jamieson, Fausset and Brown on Mark 13:15

15. And let him that is on the housetop not get down into the house, neither enter therein, to take any thing out of his house--that is, let him take the outside flight of steps from the roof to the ground; a graphic way of denoting the extreme urgency of the case, and the danger of being tempted, by the desire to save his property, to delay till escape should become impossible.