8 Then Amalek came and made war on Israel in Rephidim. 9 And Moses said to Joshua, Get together a band of men for us and go out, make war on Amalek: tomorrow I will take my place on the top of the hill with the rod of God in my hand. 10 So Joshua did as Moses said to him, and went to war with Amalek: and Moses, Aaron, and Hur went up to the top of the hill. 11 Now while Moses' hand was lifted up, Israel was the stronger: but when he let his hand go down, Amalek became the stronger. 12 But Moses' hands became tired; so they put a stone under him and he took his seat on it, Aaron and Hur supporting his hands, one on one side and one on the other; so his hands were kept up without falling till the sun went down. 13 And Joshua overcame Amalek and his people with the sword.
Matthew Henry's Commentary on Exodus 17:8-13
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.