Exodus 17:9

And Moses said unto Joshua, Choose us out men, and go out, fight with Amalek: to morrow I will stand on the top of the hill with the rod of God in mine hand.

And Moses said unto Joshua,.... The son of Nun, who was his minister, and was a man of war from his youth, trained up in the art of war, and afterwards succeeded Moses, and was captain of the armies of Israel, and fought at the head of them, and subdued the Canaanites. Moses knew he was a fit person for the present purpose, and therefore gave him the following orders:

Choose us out men; the stoutest and most courageous, best able to bear arms, and engage in war; for the multitude in common was not qualified for such service, nor was there any necessity of engaging them all in it:

and go out; out of the camp, and meet them at some distance, that the women and children might not be terrified with the enemy:

fight with Amalek; for their cause was just, Amalek was the aggressor, Israel was on the defensive part; and should it be asked where they had arms to fight with, it may be remembered that the Egyptian army that was drowned in the Red sea, and whose bodies were cast upon the shore, might furnish them with a large quantity of armour, which they stripped them of, and arrayed themselves with:

tomorrow I will stand upon the top of the hill, with the rod of God in my hand: on the top of Mount Horeb or Sinai, where he might be seen by the army of Israel with that rod in his hand, lifted up as a banner, by which God had done so many wonderful things; and by which they might be encouraged to hope that victory would go on their side, and this he promised to do "tomorrow", the day following; for sooner a select body of men could not be taken out from the people, and accoutred for war, and go forth to meet the enemy.