Exodus 19:9, 20, 24

The LORD said to Moses, “I am going to come to you in a dense cloud, so that the people will hear me speaking with you and will always put their trust in you.” Then Moses told the LORD what the people had said.

The LORD descended to the top of Mount Sinai and called Moses to the top of the mountain. So Moses went up

The LORD replied, “Go down and bring Aaron up with you. But the priests and the people must not force their way through to come up to the LORD, or he will break out against them.”