There is no immediate reason given why the number appointed should be seventy; but it is remarkable that the LORD JESUS in after ages appointed seventy disciples by way of aid to the apostles. And the Sanhedrim, which was the great court of the Jews, consisted of the same number. Luke 10:1.
Related Commentaries of Numbers 11:16
Numbers 11:16
16 And the LORD said unto Moses, Gather unto me seventy men of the elders of Israel, whom thou knowest to be the elders of the people, and officers over them; and bring them unto the tabernacle of the congregation, that they may stand there with thee.