A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jos 1:1THE LORD APPOINTS JOSHUA TO SUCCEED MOSES. (Jos. 1:1-18)
Now after the death of Moses--Joshua, having been already appointed and designated leader of Israel (Num 27:18-23), in all probability assumed the reins of government immediately "after the death of Moses."
the servant of the Lord--This was the official title of Moses as invested with a special mission to make known the will of God; and it conferred great honor and authority.
the Lord spake unto Joshua--probably during the period of public mourning, and either by a direct revelation to the mind of Joshua, or by means of Urim and Thummim (Num 27:21). This first communication gave a pledge that the divine instructions which, according to the provisions of the theocracy, had been imparted to Moses, would be continued to the new leader, though God might not perhaps speak to him "mouth to mouth" (Num 12:8).
Joshua--The original name, Oshea, (Num 13:8), which had been, according to Eastern usage, changed like those of Abram and Sarai (Gen 17:5-15) into Jehoshua or Joshua (that is, "God's salvation") was significant of the services he was to render, and typified those of a greater Saviour (Heb 4:8).
Moses' minister--that is, his official attendant, who, from being constantly employed in important services and early initiated into the principles of the government, would be well trained for undertaking the leadership of Israel.
jos 1:2now therefore arise, go over this Jordan--Joshua's mission was that of a military leader. This passage records his call to begin the work, and the address contains a literal repetition of the promise made to Moses (Deu 11:24-25; Deu 31:6-8, Deu 31:23).
jos 1:3Every place that the sole of your foot shall tread upon that have I given you--meaning, of course, not universal dominion, but only the territory comprised within the boundaries here specified (see on Deu 19:8).
jos 1:4all the land of the Hittites--These occupied the southern extremities and were the dominant tribe of Canaan. Their superior power and the extent of their dominions are attested by the mention of them under the name of Khita, on the Assyrian inscriptions, and still more frequently on the Egyptian inscriptions of the eighteenth and nineteenth Dynasties. What life and encouragement must have been imparted to Joshua by the assurance that his people, who had been overwhelmed with fear of that gigantic race, were to possess "all the land of the Hittites"!
jos 1:5There shall not any man be able to stand before thee--Canaan was theirs by a divine grant; and the renewed confirmation of that grant to Joshua when about to lead the people into it, intimated not only a certain but an easy conquest. It is remarkable, however, that his courage and hope of victory were made to depend (see on Deu 17:18) on his firm and inflexible adherence to the law of God, not only that regarding the extirpation of the Canaanites, but the whole divine code.
jos 1:10Then Joshua commanded the officers of the people--These were the Shoterim (see on Exo 5:6; Deu 20:5).
jos 1:11command the people, saying, Prepare you victuals--not manna, which, though it still fell, would not keep; but corn, sheep, and articles of food procurable in the conquered countries.
for within three days ye shall pass over this Jordan--that is, the third day, according to Hebrew idiom--the time allotted for getting ready before the encampment in Abel-Shittim broke up and they removed to the desert bank of the river where no victuals were available. At the same time Joshua himself convened the two and a half tribes which had settled east of Jordan, to remind them of their promise (Num. 32:1-42) to assist their brethren in the conquest of western Canaan. Their readiness to redeem their pledge and the terms in which they answered the appeal of Joshua displayed to great advantage their patriotic and pious feelings at so interesting a crisis.
jos 1:14ye shall pass . . . armed--that is, officered or marshalled under five leaders in the old and approved caravan order (see on Exo 13:18).
all the mighty men of valour--The words are not to be interpreted strictly as meaning the whole, but only the flower or choice of the fighting men (see on Jos 4:12).