The sad predicament of Moses on this occasion is partly traceable to the fact that he had to face alone the murmurs and complaints of the people without the accustomed assistance of the seventy elders. Since the exodus from Egypt the seventy elders of the people had always been at his side, but these had recently been killed by the fire from heaven at Taberah, so that he now stood all alone. This death overtook the elders because like Nadab and Abihu they had not shown sufficient reverence in ascending Mount Sinai on the day of the revelation, when, in view of the Divine vision, they conducted themselves in an unseemly manner. Like Nadab and Abihu the elder would have received instantaneous punishment for their offense, had not God been unwilling to spoil the joyful day of the revelation by their death. But they had to pay the penalty nevertheless: Nadab and Abihu, by being burned at the consecration of the Tabernacle, and the elders similarly, at Taberah. 
As Moses now utterly refused to bear the burden of the people alone, God said to him: "I gave thee sufficient understanding and wisdom to guide My children alone, that thou mightest be distinguished by this honor. Thou, however, wishest to share this guidance with others. Go, then, and expect no help from Me, 'but I will take of the spirit that is upon thee and will put it upon them; and they shall bear the burden of the people with thee, that thou bear it not thyself alone'" 
God bade Moses choose as his helpers in the guidance of the people such men as had already been active leaders and officers in Egypt. In the days of Egyptian bondage it frequently happened that the officers of the children of Israel were beaten if the people had not fulfilled their task in making bricks, but "he that is willing to sacrifice himself for the benefit of Israel shall be rewarded with honor, dignity, and the gift of the Holy Spirit." The officers suffered in Egypt for Israel, and were now found worthy of having the Holy Spirit come upon them.  God moreover said to Moses: "With kindly words welcome the elders to their new dignity, saying, 'Hail to you that are deemed worthy by God of being fit for this office.' At the same time, however, speak seriously with them also, saying, 'Know ye that the Israelites are a troublesome and stiff-necked people, and that you must ever be prepared to have them curse you or cast stones at you'"
God commanded the selection of the elders to take place at the Tabernacle, that Israel might reverence them, saying, "Surely these are worthy men," but they were not permitted with Moses to enter the Tabernacle and hear God's word. The people were however mistaken in assuming that God's word reached the ears of the elders, for He spoke with Moses alone, even though the prophetic spirit came upon them also. 
Now when Moses wished to proceed to the selection of the seventy elders, he was in a sore predicament because he could not evenly divide the number seventy among the twelve tribes, and was anxious to show no partiality to one tribe over another, which would lead to dissatisfaction among Israel. Bezalel, son of Uri, however, gave Moses good advice. He took seventy slips of paper on which was written "elder," and with them two blank slips, and mixed all these in an urn. Seventy-two elders, six to each tribe, now advance and each drew a slip. Those whose slips were marked "elder" were elected, while those who had drawn blank slips were rejected, but in such a wise that they could not well accuse Moses of partiality. 
By this method of appointment, it came to pass that there were six elders for each tribe except the tribe of Levi. The names of those chosen were: from the tribe of Reuben, - Hanoch, Carmi, Pallu, Zaccur, Eliab, Nemuel; from the tribe of Simeon, - Jamin, Jachin, Zohar, Ohad, Shaul, Zimri; from the tribe of Levi, - Amram, Hananiah, Nethanel, Sithri; from the tribe of Judah, - Zerah, Dan, Jonadab, Bezalel, Shephatiah, Nahshon; from the tribe of Issachar,
Moses gathered these seventy elders of novel extraction and of lofty and pious character round about the tent in which God used to reveal Himself, bidding thirty of them take their stand on the south side, thirty on the northern, and ten on the eastern, whereas he himself stood on the western side. For this tent was thirty cubits long and ten cubits wide, so that a cubit each was apportioned to the elders.  God was so pleased with the appointment of the elders that, just as on the day of the revelation, He descended from heaven and permitted the spirit of prophecy to come upon the elders, so that they received the prophetic gift to the end of their days, as God had put upon them of the spirit of Moses. But Moses' spirit was not diminished by this, he was like a burning candle from which many others are lighted, but which is not therefore diminished; and so likewise was the wisdom of Moses unimpaired. Even after the appointment of the elders did Moses remain the leader of the people, for he was the head of this Sanhedrin of seventy members which he guided and directed. 
The position of the elders was not of the same rank as that of Moses, for he was the king of Israel, and it was for this reason that God had bidden him to secure trumpets, to use them for the calling of the assembly, that this instrument might be blown before him as before a king. Hence shortly before Moses' death these trumpets were recalled from use, for his successor Joshua did not inherit from him either his kingly dignity or these royal insignia. Not until David's time were the trumpets used again which Moses had fashioned in the desert.