Jamieson, Fausset and Brown on Joshua 7:10-15

10-15. the Lord said unto Joshua, Get thee up--The answer of the divine oracle was to this effect: the crisis is owing not to unfaithfulness in Me, but sin in the people. The conditions of the covenant have been violated by the reservation of spoil from the doomed city; wickedness, emphatically called folly, has been committed in Israel (Psa 14:1), and dissimulation, with other aggravations of the crime, continues to be practised. The people are liable to destruction equally with the accursed nations of Canaan (De 7:26). Means must, without delay, be taken to discover and punish the perpetrator of this trespass that Israel may be released from the ban, and things be restored to their former state of prosperity.