Special clouds accompanied our ancestors already from the time of Avraham and Sarah. In the Exodus from Egypt, the accompaniment of the cloud takes on national significance, and in our parasha, the matter is specifically stressed.
The p’sukim that introduce the presentation of the Ten Commandments at Sinai (Shemot 19:3-9) caused the commentaries to work very hard. The order is as follows: Moshe went up the mountain, where Hashem told him the significance of Bnei Yisrael accepting the Torah and becoming a special nation. Moshe told the elders the words (devarim) of Hashem. The nation accepted the matter and Moshe informed Hashem (pasuk 8). Hashem told Moshe that He would be coming to speak to him in front of the people so that the people would believe in Moshe. It ends off: “Moshe told (vayaged) the words of the nation to Hashem” (pasuk 9).