Sforno on Numbers 12:15/ספורנו על במדבר י״ב:ט״ו

1והעם לא נסע, even though the cloud had lifted off the encampment and the Tabernacle. The Torah writes: ובהעלות הענן מעל המשכן יסעו בני ישראל בכל מסעיהם, “when the cloud would lift from above the Tabernacle the Children of Israel would begin all their respective journeys.” They did not journey on this occasion as they realised that the reason why the cloud had lifted was in order to distance itself from the tzoraat.