Moses went up into the mount of God, to the place where God had now fixed his cloudy pillar, and where he was about to manifest himself in a glorious manner. So it is an anticipation.
Related Commentaries of Exodus 19:3
Exodus 19:3
3 And Moses went up unto God, and the LORD called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel;