They travelled from Rephidim, came into to the wilderness of Sinai, and set up camp in the wilderness. Israel camped there, right in front of the mountain.
Now Moses was tending the flock of his father-in-law Jethro, the priest of Midian. So he led the flock to the farthest end of the wilderness, coming to the mountain of God, Horeb.
So He said, “I will surely be with you. So that will be the sign to you that it is I who have sent you. When you have brought the people out of Egypt: you will worship God on this mountain.”