Exodus 19:1

1 In the third month, when the children of Israel were gone forth out of the land of Egypt, the same day came they into the wilderness of Sinai.
The King James Version is in the public domain.

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.
The King James Version is in the public domain.