2 Samuel 18:24

And David sat between the two gates
Of the city of Mahanaim; which being a fortified place had two walls, one within another, and in each wall a gate; and between these David sat, waiting for news of the battle:

and the watchman went up to the roof over the gate unto the wall;
the gate to the outward wall, over which was a tower, and on that a flat roof; to which the watchman went to observe if he could see an express coming; no doubt by David's orders:

and lifted up his eyes and looked;
that is, very diligently and wistfully:

and, behold, a man running alone:
which made him the more observable, and was the more likely to be a messenger.