Midrash su Esodo 19:24

2) "Moses called to Aaron and to his sons": Because the L–rd honored Aaron at first, so, Moses honored him afterwards. Where is it seen that the L–rd honored him at first? In (Shemoth 19:24): "And go up, you and Aaron with you" — so, Moses honored him afterwards, viz.: "Moses called to Aaron and to his sons and (only afterwards) to the elders of Israel."

… it is written there “Behold the heaven and the heaven of heavens cannot contain You…” (Melachim I 8:27) and here it is written “…the glory of the Lord filled the Tabernacle.” (Shemot 40:35) R’ Yehoshua of Sachnin said in the name of R’ Levi ‘to what is this likened? To an open cave at the edge of the sea. When the sea storms the cave is filled, but the sea is not reduced. So too, even though it is written that ‘the glory of the Lord filled the Tabernacle’ the upper and lower worlds did not lose anything of the brilliance of the glory of the Holy One, just as it is written “Do I not fill the heavens and the earth? says the Lord.” (Yirmiyahu 23:24) Therefore it is written here ‘And it was’. Just as the Divine Presence was here below at the beginning of the creation of the world but withdrew to above, now it returned to be below as it had been “And it was that on the day that Moses finished…” (Bamidbar 7:1) ... [Another explanation. “And it was that on the day that Moses finished erecting the Mishkan…” (Numbers 7:1)] R’ Simon said: at the time when the Holy One told Israel to erect the Tabernacle, He hinted that when the Tabernacle below is erected, the Tabernacle above is erected, as it says “And it was that on the day that Moses finished…” (ibid.) It does not say ‘erecting the Tabernacle’ but rather ‘erecting this (et) the Tabernacle.’ This refers to the Tabernacle above. The Holy One said: in this world, when the Tabernacle was erected, I commanded Aharon and his sons that they bless you. In the time to come I, in my glory, will bless you. So it is written “May the Lord bless you from Zion, He Who made heaven and earth.” (Psalms 134:3)

(The Holy One, blessed be He, said:) Let Moses descend to the camp, and afterwards will I cause My Torah to be proclaimed. He said to him: "Go down, charge the people" (Ex. 19:21). Moses was wishing to be || there, and he said to Him: I have already charged the people. He said to him: Go, and call thy Rabbi. Moses descended to the camp to call Aaron, and the Holy One, blessed be He, proclaimed His Torah unto His people, as it is said, "So Moses went down unto the people, and told them" (Ex. 19:25). What is written after this? "And God spake all these words, saying, I, the Lord, am (to be) thy God, who brought thee out of the land of Egypt, out of the house of bondage" (Ex. 20:1, 2).

Similarly the Holy-One-Blessed-be-He said to Moses: "Now leave Me alone." Said Moses: The Holy-One-Blessed-be-He wants me to make peace between Him and Israel. That is why He says: "Now--leave Me alone". So he promptly began to intercede on their behalf.