Then the cloud covered the tent of meeting, and the glory of the Lord filled the tabernacle.
Moses was not able to enter the tent of meeting because the cloud settled upon it, and the glory of the Lord filled the tabernacle.
Whenever the cloud was taken up from the tabernacle, the Israelites would set out on each stage of their journey;
but if the cloud was not taken up, then they did not set out until the day that it was taken up.
For the cloud of the Lord was on the tabernacle by day, and fire was in the cloud by night, before the eyes of all the house of Israel at each stage of their journey.
References for Exodus 40:38