2 Samuel 17:17
Now Jonathan and Ahimaaz stayed by En–rogel; for they might not be seen to come into the city: and a wench went and told them; and they went and told king David.
Cross-references
In 2 Samuel 15:36, David instructs the priests to use their sons as messengers, directly establishing the spy network seen here.
2 Samuel 18:19 continues Ahimaaz's story as he volunteers to bring news to David after the battle.
1 Kings 1:42 shows Jonathan, the other spy, later appearing in Adonijah's camp as a trusted messenger.
Joshua 15:7 mentions En-rogel in a boundary description, confirming the geographical location of the spies' hiding place.
Joshua 18:16 also lists En-rogel in the tribal border, reinforcing the same location as in the main verse.
1 Kings 1:9 records Adonijah's feast at En-rogel, showing the same place used later for a very different event.
Acts 23:16 parallels this covert messaging: Paul's nephew relays a plot, similar to the servant/spy relay here.