Be strong and of good courage; for you shall cause this people to inherit the land which I swore to their fathers to give them.
"According to all the law  ..." Yes, indeed, according to this testimony, even in the days of Joshua, there was a "Law of Moses," containing all that the Israelites were expected to do!  Efforts to make the Pentateuch itself a late book by dating from the times of the judges, or the monarchy, or the post-exilic priesthood are among the most stupid and impossible tasks the so-called "higher critics" ever assigned themselves!  This is as good a place as any to take a little closer look at what the Word of God says concerning this: