In the third month, on the same day [of the month] that the Israelites had left the land of Egypt, they entered the Wilderness of Sinai.
References for Exodus 19:1
After they departed from Rephidim, they entered the Wilderness of Sinai and camped in the wilderness, and Israel camped there in front of the mountain.
Moses went up [the mountain] to God, and the Lord called to him from the mountain: "This is what you must say to the house of Jacob, and explain to the Israelites:
You have seen what I did to the Egyptians and how I carried you on eagles' wings and brought you to Me.
Now if you will listen to Me and carefully keep My covenant, you will be My own possession out of all the peoples, although all the earth is Mine,
References for Exodus 19:5
and you will be My kingdom of priests and My holy nation. These are the words that you are to say to the Israelites."
References for Exodus 19:6