Charles Ellicott Commentary Numbers 9:17

"And whenever the cloud was taken up from over the Tent, then after that the children of Israel journeyed: and in the place where the cloud abode, there the children of Israel encamped." — Numbers 9:17 (ASV)

And when the cloud was taken up... —Only one instance is recorded of disregard of the Divine direction so miraculously granted, namely, in Numbers 14:40-42. It was necessary that the hosts of Israel should always be in a watchful state, and ready to obey at once the indications given to them of the Divine will, thus providing a striking type and pattern to the Christian Church, and teaching it, both collectively and individually, to seek and to follow the guidance of its Divine Head, whose promise is Lo, I am with you alway, even unto the end of the world.