Moses said unto Joshua. — This is the first mention of Joshua. He was an Ephraimite, the son of a man called Nun, and the tenth in descent from Joseph (see Note on Exodus 6:16), in the prime of life — about 45 years old — and probably known as possessing military capacity. His actual name at the timo was Hoshea, which might have been viewed as a good omen, since the word meant “Saviour.” Moses afterwards changed his name to Jehoshua (Numbers 13:16), which became by contraction Joshua. We find him, later in Exodus, acting as Moses’ personal attendant, or “minister” (Numbers 24:13; Numbers 32:17; Numbers 33:11), accompanying him to the top of Sinai, and placed by him in charge of the first “Tabernacle.” Afterwards he, with Caleb, was the only one of the spies who brought back a true report of Canaan. (Numbers 14:6-9.) His choice as leader to succeed Moses resulted naturally from his antecedents, and is related in Numbers 27:18-23.
Choose us out men. — The weakness of Israel was in its unwieldy numbers. Moses saw this, and, after deciding that he was himself unfit for battle, and passing the command on to Joshua, made the one suggestion that a select body of troops should be employed against the assailants. The advice was good, and “Joshua did as Moses had said to him” (Exodus 17:10).
I will stand on the top of the hill. — A particular “hill” was no doubt meant — a “hill,” and not a mountain. But the exact scene of the battle is too uncertain to make it possible to fix on any one particular eminence.