Only be strong and very courageous, to observe to do according to all the law, which Moses my servant commanded you: don't turn from it to the right hand or to the left, that you may have good success wherever you go.
JOSHUA: We do not even get out of the first chapter until we find this clear and undeniable reference to the "Law which Moses my servant commanded."  If that is not the Law of Moses - ALL of it - the entire Pentateuch, then it is nothing at all!  We reject the arbitrary arrogance with which so-called "scholars" would try to limit this to some little fraction of the Mosaic Law.  There is no objective grounds whatever for such an obviously false maneuver.