John Gill Commentary Numbers 9:21

"And sometimes the cloud was from evening until morning; and when the cloud was taken up in the morning, they journeyed: or [if it continued] by day and by night, when the cloud was taken up, they journeyed." — Numbers 9:21 (ASV)

And [so] it was when the cloud abode from even unto the
morning
The whole night, during which time they rested in their beds:

and [that] the cloud was taken up in the morning, then they journeyed ;
whether [it was] by day or night that the cloud was taken up, they
journeyed ;
whether at morning or midnight; for sometimes, as Aben Ezra observes, they travelled in the night; whensoever
their sentinels gave notice that the cloud was taken up, even though at midnight, they arose and prepared for
their journey; and by this it is evident, that the appearance by day and night was the same body called the
cloud, though beheld in a different view, in the daytime as a cloud, in the nighttime as fire.