Geshem the Arabian, elsewhere called Gashmu (Nehemiah 6:6), may have been an independent sheikh possessing authority in Idumea, or in the desert country adjoining upon Ammon; but it seems quite as likely that he was merely the head of a body of Arab troops maintained by Sanballat at Samaria (Nehemiah 4:7).
Sanballat, Tobiah, and Geshem are united so closely, and act so much together (Nehemiah 4:1-7; Nehemiah 6:1, Nehemiah 6:2, Nehemiah 6:6, Nehemiah 6:12, Nehemiah 6:14), that it is difficult to suppose them to be three chieftains residing on three sides of Judaea, the north, the east, and the south, merely holding diplomatic intercourse with each other, which is the ordinary idea.
Note that Tobiah is present with Sanballat in Samaria on one occasion (Nehemiah 4:3), and that Geshem and Sanballat propose a joint interview with Nehemiah on another (Nehemiah 6:2). They laughed us to scorn, and said.
Either by messengers, like Sennacherib (2 Kings 18:17-35), or by a formal written communication, as Ewald supposes. Will ye rebel? Compare Nehemiah 6:6; and see also Ezra 4:12-16. Had Artaxerxes not granted permission, Nehemiah's proceedings might naturally have borne this interpretation.