Charles Ellicott Commentary Exodus 40:34

"Then the cloud covered the tent of meeting, and the glory of Jehovah filled the tabernacle." — Exodus 40:34 (ASV)

THE DESCENT OF THE GLORY OF GOD UPON THE TABERNACLE.

Then a cloud. —Hebrew, the cloud, that is, the same cloud that had accompanied the host and directed their journeys from Succoth (Exodus 13:20–22).

Covered the tent. —The cloud rested on the tent outside; the “glory of God,”—some ineffably brilliant appearance—entered inside, and “filled” the entire dwelling. It pleased God in this way to manifest His intention of fulfilling His promise to go with the people in person (Exodus 33:17).