8 And Amalek cometh, and fighteth with Israel in Rephidim, 9 and Moses saith unto Joshua, 'Choose for us men, and go out, fight with Amalek: to-morrow I am standing on the top of the hill, and the rod of God in my hand.' 10 And Joshua doth as Moses hath said to him, to fight with Amalek, and Moses, Aaron, and Hur, have gone up 'to' the top of the height; 11 and it hath come to pass, when Moses lifteth up his hand, that Israel hath been mighty, and when he letteth his hands rest, that Amalek hath been mighty. 12 And the hands of Moses 'are' heavy, and they take a stone, and set 'it' under him, and he sitteth on it: and Aaron and Hur have taken hold on his hands, on this side one, and on that one, and his hands are stedfast till the going in of the sun; 13 and Joshua weakeneth Amalek and his people by the mouth of 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.