So there went one on horseback to meet him, and said, Thus saith the king, Is it peace? And Jehu said, What hast thou to do with peace? turn thee behind me. And the watchman told, saying, The messenger came to them, but he cometh not again. (2 Kings 9:18)
The watchman kept his eyes on the approaching group, seeking to discover whether their intentions were friendly or otherwise. The messenger whom Joram had sent was supposed to return with his report. When he failed to do so, the action might be regarded as an indication that the approaching group was not coming on a friendly mission. It was the province of the watchman to report what he saw, not to issue orders, and he immediately reported to the king that his messenger was not coming back.
Turn thee behind me.
The messenger ascertained only too well that Jehu’s mission was not one of peace, but he was to be given no opportunity to return and convey such a message to the king. Instead, he was ordered to fall to the rear while the men continued their advance.