The Priesthood Organized.--Moses was of the Tribe of Levi, and son-in-law to Jethro the Midianite. The Midianites were descended from Midian, the fourth son of Abraham by his wife Keturah. [4] It was from Jethro that Moses received the Melchizedek Priesthood. [5] Thus qualified, the Israelite leader organized, by divine direction, the Lesser Priesthood, with his brother Aaron at its head. [6] Aaron's sons, Nadab, Abihu, Eleazer and Ithamar, were associated with him in the priest's office. [7] Idolatry and Expiation.--Just prior to their setting apart as priests, and while Moses, with faithful Joshua, was up in the Mount, receiving the Law and the Testimony, Israel lapsed temporarily into idolatry. In the golden calf, which they persuaded Aaron to make for them, they worshiped the Egyptian god Apis, or, as Dr. Geikie suggests, the ox-headed god of the Asiatics. This sin demanded and received prompt punishment. By command of Moses, the tribe of Levi--every man of which responded to his loyal appeal, "Who's on the Lord's side?"--slew with the sword three thousand males among the idolaters. The stern expiation complete, the work of organization proceeded. The Levites--As an act coordinate with the destruction of Egypt's first-born, the Lord had chosen the first-born males of all the families of Israel, and had set them apart for a special purpose. He now took the tribe of Levi, instead, and made of them the sacerdotal class of the nation; a reward, no doubt, for the zeal they had displayed in wiping out the stain of idolatry from Israel. The laws of Moses were then promulged and codified, and the sublime system of heaven-revealed religion was set in motion. A Nation on the March.--All being ready for the great march Zionward, the Camp of Israel struck its tents, and, guided by the Cloud and Pillar of Fire, moved majestically through the Sinaitic desert toward the Wilderness of Paran. The descendants of Jacob numbered at that time nearly three million souls, including an army of half a million. They were divided into four camps of three tribes each, exclusive of the Levites; Joseph being twice numbered in Ephraim and Manasseh, thus making up for the absence of the sacred class from the tribal count. Foremost rose aloft the lion standard of Judah, the future kingly power, out of which was to come the Savior-King of Israel. Then followed the tribes and armies of Issachar and Zebulon, and after them the sons of Gershon and Merari (first and third sons of Levi), bearing the components of the Tabernacle, which it was their duty to set up and take down, as the Camp rested or resumed its journey. The standard of Reuben was next advanced, and immediately in his rear marched Simeon and Gad. The Ark then appeared, borne in the very center of the moving host on the shoulders of the sons of Kohath. Ephraim and Manasseh followed; then Benjamin; the tribes of Dan, Ashur and Naphtali bringing up the rear.