Numbers 2:17-18

17And the tent of meeting shall set forth, the camp of the Levites in the midst of the camps; as they encamp, so shall they set forth, every man in his place, according to their standards.

18The standard of the camp of Ephraim according to their hosts shall be westward; and the prince of the sons of Ephraim shall be Elishama the son of Ammihud;