Exodus 19 11
and be ready on the third day because that is when the Lord will descend upon Mount Sinai in the full view of everyone.
Compare with other 3 random translations
NKJ Exodus 19:11And let them be ready for the third day. For on the third day the Lord will come down upon Mount Sinai in the sight of all the people.
EAS Exodus 19:11They must be ready on the third day. On that day, I will come down on Sinai mountain, so that all the people see me.
NIV Exodus 19:11and be ready by the third day, because on that day the Lord will come down on Mount Sinai in the sight of all the people.