'River' in the Bible

Moreover I said to the king, "If it pleases the king, let letters be given me to the governors beyond the River, that they may let me pass through until I come to Judah;

Then I came to the governors beyond the River, and gave them the king's letters. Now the king had sent with me captains of the army and horsemen.

Next to them repaired Melatiah the Gibeonite, and Jadon the Meronothite, the men of Gibeon, and of Mizpah, [that appertained] to the throne of the governor beyond the River.