The watchman, as his duty was, had sent immediate notice to the king that he saw a crowd approaching (see 2 Kings 9:17-20). Jonadab, who was with the king, was prompt to give the explanation.
Related Commentaries of 2 Samuel 13:35
2 Samuel 13:35
35 And Jonadab said unto the king, Behold, the king's sons come: as thy servant said, so it is.