8 While the people of Israel were still at Rephidim, the warriors of Amalek attacked them. 9 Moses commanded Joshua, "Choose some men to go out and fight the army of Amalek for us. Tomorrow, I will stand at the top of the hill, holding the staff of God in my hand." 10 So Joshua did what Moses had commanded and fought the army of Amalek. Meanwhile, Moses, Aaron, and Hur climbed to the top of a nearby hill. 11 As long as Moses held up the staff in his hand, the Israelites had the advantage. But whenever he dropped his hand, the Amalekites gained the advantage. 12 Moses' arms soon became so tired he could no longer hold them up. So Aaron and Hur found a stone for him to sit on. Then they stood on each side of Moses, holding up his hands. So his hands held steady until sunset. 13 As a result, Joshua overwhelmed the army of Amalek in battle. 14 After the victory, the Lord instructed Moses, "Write this down on a scroll as a permanent reminder, and read it aloud to Joshua: I will erase the memory of Amalek from under heaven." 15 Moses built an altar there and named it Yahweh-Nissi (which means "the Lord is my banner"). 16 He said, "They have raised their fist against the Lord 's throne, so now the Lord will be at war with Amalek generation after generation."
Matthew Henry's Commentary on Exodus 17:8-16
Commentary on Exodus 17:8-16
(Read Exodus 17:8-16)
Israel engaged with Amalek in their own necessary defence. God makes his people able, and calls them to various services for the good of his church. Joshua fights, Moses prays, both minister to Israel. The rod was held up, as the banner to encourage the soldiers. Also to God, by way of appeal to him. Moses was tired. The strongest arm will fail with being long held out; it is God only whose hand is stretched out still. We do not find that Joshua's hands were heavy in fighting, but Moses' hands were heavy in praying; the more spiritual any service is, the more apt we are to fail and flag in it. To convince Israel that the hand of Moses, whom they had been chiding, did more for their safety than their own hands, his rod than their sword, the success rises and falls as Moses lifts up or lets down his hands. The church's cause is more or less successful, as her friends are more or less strong in faith, and fervent in prayer. Moses, the man of God, is glad of help. We should not be shy, either of asking help from others, or of giving help to others. The hands of Moses being thus stayed, were steady till the going down of the sun. It was great encouragement to the people to see Joshua before them in the field of battle, and Moses above them on the hill. Christ is both to us; our Joshua, the Captain of our salvation, who fights our battles, and our Moses, who ever lives, making intercession above, that our faith fail not. Weapons formed against God's Israel cannot prosper long, and shall be broken at last. Moses must write what had been done, what Amalek had done against Israel; write their bitter hatred; write their cruel attempts; let them never be forgotten, nor what God had done for Israel in saving them from Amalek. Write what should be done; that in process of time Amalek should be totally ruined and rooted out. Amalek's destruction was typical of the destruction of all the enemies of Christ and his kingdom.