Midrash su Esodo 30:36

2) The limitations: (Bamidbar 7:89): "And when Moses came to the ohel moed (for the L–rd) to speak to 1 him, that he heard the voice speaking to 2 him … and He spoke to him." (Shemoth 25:22): "And I will be appointed for you there, and I will speak to you … all that I will charge you with to the children of Israel." (Shemoth 29:42): "… where I shall appoint a time for you (plural) to speak to you (singular) there." (Shemoth 30:6):

6) — But let this exclude only Israel, who were not found fit to ascend Mount Sinai, but not the elders, who were found fit to do so! (viz. [Shemoth 24:1]: "And to Moses He said: Go up … and seventy of the elders of Israel.") Let it exclude the elders, who were not present at the L–rd's dibbur to Moses (on Mount Sinai after the giving of the Torah, viz. [Shemoth 24:14]: "Abide for us here," in the encampment, with the rest of the people), and not the sons of Aaron, who were present at the L–rd's dibbur to Moses. Let it exclude the sons of Aaron, who were not together with Moses for dibbur, and not Aaron, who was together with Moses for dibbur (viz.: "And the L–rd spoke to Moses and to Aaron" — and not to his sons). It is, therefore, written (Vayikra 30:6): "… where I shall be appointed for you" — For you there was appointment, but not for (any) of the others.