Shemot 24:16

ויכסהו הענן AND THE CLOUD COVERED IT (lit., “him”) [SIX DAYS] — Our Rabbis are of different opinions as to what this passage means. Some of them hold that these were the six days from the first of Sivan (until the Feast of Weeks, the day of the Giving of the Law) — and that the word ויכסהו in the phrase ויכסהו הענן “the cloud covered him” or covered “it” means that it covered the mountain. ויקרא אל משה ביום השביעי AND HE CALLED UNTO MOSES ON THE SEVENTH DAY of Sivan to utter the Ten Commandments. It is true that Moses and all Israel were standing there but the text states, “He called unto Moses” merely to give special honour to Moses calling him by name. Others, however, say that the passage means: AND THE CLOUD COVERED HIM — Moses, FOR SIX DAYS after the Ten Commandments had been given. These were at the beginning of the forty days which Moses spent on Mount Sinai when he went up to receive the Tablets, and Scripture teaches you that whosoever enters the camp of the Divine Majesty (here the mountain and later on the Holy of Holies) requires separation from others (must live in seclusion) for six days (Yoma 4a).

וַיִּשְׁכֹּ֤ן כְּבוֹד־יְהֹוָה֙ עַל־הַ֣ר סִינַ֔י וַיְכַסֵּ֥הוּ הֶעָנָ֖ן שֵׁ֣שֶׁת יָמִ֑ים וַיִּקְרָ֧א אֶל־מֹשֶׁ֛ה בַּיּ֥וֹם הַשְּׁבִיעִ֖י מִתּ֥וֹךְ הֶעָנָֽן׃

And the glory of the Lord rested upon mount Sinay, and the cloud covered it for six days: on the seventh day he called to Moshe out of the midst of the cloud.