SEVENTY DISCIPLES. Luke 10:1-16 records the sending out of seventy disciples by Jesus as a part of His extended journey to Jerusalem. The number seventy was symbolic to the Jews. It suggested the number of elders that Moses had chosen to help with the task of leading Israel in the wilderness (Num 11:16, 17, 24, 25). It was also (perhaps because of Moses’ selection of seventy elders in the wilderness) the number of the members of the Sanhedrin, the supreme council of the Jews (though that number has been fixed at seventy-one or seventy-two by some). It was also the “number” of the nations in the world (see Gen 10, the LXX has seventy-two), coming from the reference to the seventy members of Jacob’s family in Egypt. Some have supposed that Jesus foreshadowed the preaching of the Gospel to all nations. As far as can be known, the event may have come close to the Feast of Tabernacles at which seventy bullocks were sacrificed, corresponding to the nations of the world. Interpreters who consider Luke to have written his gospel on the pattern of the Pentateuch find this passage to be represented by the Book of Numbers in that body of writings.
International Standard Bible Encyclopedia (1915)
The account of the designation and mission of these is found only in Luke 10. Some have therefore sought to maintain that we have here only a confused variant of the appointment of the Twelve; but this is impossible in the light of Luke’s account of the Twelve in chapter 9.
The documents vary as between the numbers seventy and seventy-two, so that it is impossible to determine which is the correct reading; and internal evidence does not help at all in this case. There is nothing in the function or circumstances to indicate any reason for the specific number.
Commentators have sought parallels in the seventy elders chosen to assist Moses (Nu 11) and suppose that Jesus was incidentally indicating Himself as the "prophet like unto Moses" whom God would raise up.
Again, the Jews popularly reckoned the "number of the nations of the earth" at seventy (compare Ge 10), and some have supposed Jesus to be thus indicating that His gospel is universal. Attention is called to the fact that the Seventy are not forbidden to go to Gentiles and that their commission probably included Peraea, where many Gentiles were to be found. Some, again, have supposed that Jesus had in mind the Jewish Sanhedrin, composed of seventy (or seventy-two), and that the appointment of a like number to extend the work of His kingdom was a parabolic recognition that as the Jews were officially rejecting Him, so He was rejecting them as agents for the work of the kingdom. It is impossible to speak with any certainty as to any of these suggestions. It is to be noted that there is the same confusion between the numbers seventy and seventy-two in all four instances, as also in the tradition as to the number of translators of the Septuagint.
Inasmuch as no further mention is made of these workers, it is to be understood that they were appointed for a temporary ministry. Tradition names several of them and identifies them with disciples active after Pentecost. While it is probable that some of these were witnesses later, the tradition is worthless in details. The mission of these and the reason assigned for their appointment are essentially the same as in the case of the Twelve. Jesus is now completing His last popular campaign in preaching and introducing the kingdom of heaven. The employing of these in this service is in line with the permanent ideal of Christianity, which makes no distinction between the "laymen" and the "clergy" in responsibility and service. Jesus was perhaps employing all whose experience and sympathy made them fit for work in the harvest that was so plenteous while the laborers were few. He found seventy such now as He would find a hundred and twenty such after His ascension (Ac 1:15).