Numbers 10:33

And they departed from the mount of the Lord three days' journey, during which time nothing of interest happened, the people seemingly being satisfied with everything that the Lord did; and the Ark of the Covenant of the Lord went before them in the three days' journey, to search out a resting-place for them, a suitable camping-ground for the entire army. It seems that the ark alone was taken from the rest of the Sanctuary appointments and carried at the head of the host, as near as possible beneath the cloud.