Come down in the sight of all the people— i.e. The cloud and darkness, declarative of the Divine Presence, will come down upon the mountain. For Jehovah himself was not otherwise visible to them. Compare Exodus 19:18; Exodus 19:20 and see Deuteronomy 4:12.
Related Commentaries of Exodus 19:11
Exodus 19:11
11 And be ready against the third day: for the third day the LORD will come down in the sight of all the people upon mount Sinai.