A prophet of the Lord - i. e. of Yahweh. It was necessary to inquire thus definitely, as there were still plenty of prophets who were only prophets of Baal 2 Kings 3:13.
Here is Elisha - Jehoram appears to have been ignorant of his presence with the host, and one of his “servants,” or officers, answered Jehoshaphat’s inquiry.
Which poured water - An act signifying ministration or attendance (compare John 13:5 ff).