Exodus 19:11

11 And let them be ready against the third day, for on the third day the Lord will descend upon mount Sina before all the people.

Exodus 19:11 Meaning and Commentary

Exodus 19:11

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 Exodus 19:16)

for the third day the Lord will come down in the sight of all the
people upon Mount Sinai;
which must be understood, consistent with his omnipresence, and is only expressive of some visible display of his power, and of some sensible token of his presence to the people; he was now upon it in the pillar of cloud, but then he would appear in another manner, and descend in a thick cloud and fire, which all the people would see, though they could not see the similitude of anything in it.

Exodus 19:11 In-Context

9 And the Lord said to Moses, Lo! I come to thee in a pillar of a cloud, that the people may hear me speaking to thee, and may believe thee for ever: and Moses reported the words of the people to the Lord.
10 And the Lord said to Moses, Go down and solemnly charge the people, and sanctify them to-day and to-morrow, and let them wash their garments.
11 And let them be ready against the third day, for on the third day the Lord will descend upon mount Sina before all the people.
12 And thou shalt separate the people round about, saying, Take heed to yourselves that ye go not up into the mountain, nor touch any part of it: every one that touches the mountain shall surely die.
13 A hand shall not touch it, for shall be stoned with stones or shot through with a dart, whether beast or whether man, it shall not live: when the voices and trumpets and cloud depart from off the mountain, they shall come up on the mountain.

The Brenton translation of the Septuagint is in the public domain.