John Gill Commentary Numbers 12:9

"And the anger of Jehovah was kindled against them; and he departed." — Numbers 12:9 (ASV)

And the anger of the Lord was kindled against them
Which might be visible by some outward token, as by lightning from the cloud, or, however, what follows was sufficient to show it:

and he departed ;
from the door of the tabernacle of the congregation, where he had stood in the pillar of cloud for some time; but as soon as he had given his testimony of Moses, and expressed his displeasure at Aaron and Miriam, he went away directly from them; not staying to hear what they had to say for themselves, which was a plain indication of his anger against them.