and be ready for the third day. For on the third day the LORD will come down on Mount Sinai in the sight of all the people.
The thick cloud prohibits curious enquiries into secret things and commands awful adoration of what is revealed. God comes down visibly so the people see His glory and are convinced He is among them. This honours Moses especially: when they hear God speak to him and see it with their own eyes, they will believe him forever.
AI summary
Commenting on Exodus 19:9-15
And be ready against the third day,.... Not the third day of the month, but the third day from hence, this being the fourth, and the morrow the fifth, and the third day, the day following that, the sixth, on which day it is generally agreed by the Jews that the law was given; see Gill on Exo 19:16.
Exo 19:10-15 God then commanded Moses to prepare the people for His appearing or speaking to them: (1) by their sanctification, through the washing of the body and clothes (see Gen 35:2), and abstinence from conjugal intercourse (Exo 19:15) on account of the defilement connected therewith (Lev 15:18); and (2) by setting bounds round the people, that they might not ascend or touch the mountain.
Commenting on Exodus 19:10-15