Now Jonathan and Ahimaaz were staying at En-rogel, where a servant girl would come and pass along information to them. They in turn would go and inform King David, for they dared not be seen entering the city.
We must now leave David's enemies pleasing themselves with the thoughts of a sure victory by following Hushai's counsel, and sending a summons, no doubt, to all the tribes of Israel, to come to the general rendezvous at a place appointed, pursuant to that counsel; and we next find David's friends consulting how to get him notice of all this, that he might steer his course accordingly.
Commenting on 2 Samuel 17:15-21
Nevertheless, a lad saw them, and told Absalom,.... Saw them conversing with the girl, and departing for David's army; according to Josephus (o), they were some horsemen that saw them about two furlongs or a quarter mile from Jerusalem, and acquainted Absalom with it: but they went both of them away quickly; made all the haste they could with their message to David: and came...
by En-rogel--the fuller's well in the neighborhood of Jerusalem, below the junction of the valley of Hinnom with that of Jehoshaphat.