Jamieson, Fausset and Brown on Joshua 5:14

14. the host of the Lord--either the Israelitish people (Ex 7:4; 12:41; Is 55:4), or the angels (Psa 148:2), or both included, and the Captain of it was the angel of the covenant, whose visible manifestations were varied according to the occasion. His attitude of equipment betokened his approval of, and interest in, the war of invasion.

Joshua fell on his face ..., and did worship--The adoption by Joshua of this absolute form of prostration demonstrates the sentiments of profound reverence with which the language and majestic bearing of the stranger inspired him. The real character of this personage was disclosed by His accepting the homage of worship (compare Ac 10:25, 26; Re 19:10), and still further in the command, "Loose thy shoe from off thy foot" (Ex 3:5).