Exodus 19:3, 20, 23

Then Moses climbed the mountain to appear before God. The LORD called to him from the mountain and said, “Give these instructions to the family of Jacob; announce it to the descendants of Israel

The LORD came down on the top of Mount Sinai and called Moses to the top of the mountain. So Moses climbed the mountain.

“But LORD,” Moses protested, “the people cannot come up to Mount Sinai. You already warned us. You told me, ‘Mark off a boundary all around the mountain to set it apart as holy.’”