Exodus 24:20 And the Lord came down upon mount Sinai, on the top of the mount: and the Lord called Moses up to the top of the mount; and Moses went up.
[Patriarchs & Prophets pp 313] Moses and “his minister Joshua” were now summoned to meet with God. And as they were to be some time absent, the leader appointed Aaron and Hur, assisted by the elders, to act in his stead. “And Moses went up into the mount, and a cloud covered the mount. And the glory of the Lord abode upon Mount Sinai.” For six days the cloud covered the mountain as a token of God's special presence; yet there was no revelation of Himself or communication of His will. During this time Moses remained in waiting for a summons to the presence chamber of the Most High.
He had been directed, “Come up to Me into the mount, and be there,” and though his patience and obedience were tested, he did not grow weary of watching, or forsake his post. This period of waiting was to him a time of preparation, of close self-examination. Even this favored servant of God could not at once approach into His presence and endure the exhibitions of His glory. Six days must be employed in devoting himself to God by searching of heart, meditation, and prayer before he could be prepared for direct communication with his Maker. Upon the seventh day, which was the Sabbath, Moses was called up into the cloud.
The thick cloud opened in the sight of all Israel, and the glory of the Lord broke forth like devouring fire. “And Moses went into the midst of the cloud, and gat him up into the mount; and Moses was in the mount forty days and forty nights.” The forty days’ tarry in the mount did not include the six days of preparation. During the six days Joshua was with Moses, and together they ate of the manna and drank of “the brook that descended out of the mount.” But Joshua did not enter with Moses into the cloud. He remained without, and continued to eat and drink daily while awaiting the return of Moses, but Moses fasted during the entire forty days.
Exodus 24:17 And the sight of the glory of the Lord was like devouring fire on the top of the mount in the eyes of the children of Israel. 18 And Moses went into the midst of the cloud, and gat him up into the mount: and Moses was in the mount forty days and forty nights.
May God add His blessing to the study of His word. "Good night" and God bless!