Charles Ellicott Commentary Numbers 16:42

"And it came to pass, when the congregation was assembled against Moses and against Aaron, that they looked toward the tent of meeting: and, behold, the cloud covered it, and the glory of Jehovah appeared." — Numbers 16:42 (ASV)

And, behold, the cloud covered it.— The cloud had probably been removed on the preceding day when the rebels were consumed, and was now again restored in order to encourage Moses and Aaron.