John Gill Commentary Joshua 5:15

"And the prince of Jehovah`s host said unto Joshua, Put off thy shoe from off thy foot; for the place whereon thou standest is holy. And Joshua did so." — Joshua 5:15 (ASV)

And the Captain of the Lord's host said to Joshua
As a trial and proof of his obedience to him:

loose your shoe from off your foot ;
which is to be understood literally, as when the like was commanded Moses at Horeb, (Exodus 3:5) ; though some interpret it figuratively; as Abarbinel, ``remove from you such thoughts that you shall take this city by strength:''

for the place where you stand [is] holy ;
because of the presence of this Person, and as long as he was there, though afterwards was as another place; the Jewish commentator, last mentioned, thinks this intimates that the city, and all in it (and all round about it), should be "cherem", devoted, and so be holy to the Lord:

and Joshua did so ;
loosed his shoe from his foot, in obedience to the Captain of the Lord's host, thereby giving proof of his readiness, willingness, and alacrity to serve under him.