Matthew Henry Commentary Exodus 17:8-16

"Then came Amalek, and fought with Israel in Rephidim. 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 my hand. So Joshua did as Moses had said to him, and fought with Amalek: and Moses, Aaron, and Hur went up to the top of the hill. And it came to pass, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed. But Moses` hands were heavy; and they took a stone, and put it under him, and he sat thereon; and Aaron and Hur stayed up his hands, the one on the one side, and the other on the other side; And his hands were steady until the going down of the sun. And Joshua discomfited Amalek and his people with the edge of the sword. And Jehovah said unto Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua: that I will utterly blot out the remembrance of Amalek from under heaven. And Moses built an altar, and called the name of it Jehovah-nissi; And he said, Jehovah hath sworn: Jehovah will have war with Amalek from generation to generation." — Exodus 17:8-16 (ASV)

Israel engaged with Amalek in their own necessary defense. God makes his people able and calls them to various services for the good of his church. Joshua fights, Moses prays, and both minister to Israel. The rod was held up as a banner to encourage the soldiers. It was also held up to God as an appeal to him.

Moses was tired. The strongest arm will fail if held out for a long time; it is God alone whose hand is still stretched out. We do not find that Joshua's hands grew heavy in fighting, but Moses' hands grew heavy in praying; the more spiritual any service is, the more prone we are to fail and falter in it. To convince Israel that the hand of Moses (whom they had been rebuking) did more for their safety than their own hands, and his rod more than their sword, 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, was glad of help. We should not be shy either of asking for help from others or of giving help to others. The hands of Moses, being thus supported, were steady until sunset.

It was a 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 for long and shall be broken at last. Moses was to write what had been done—what Amalek had done against Israel; he was to write their bitter hatred; and he was to write their cruel attempts. Let these never be forgotten, nor what God had done for Israel in saving them from Amalek.

He was also to write what should be done: that in the course of time Amalek should be totally ruined and rooted out. Amalek's destruction was a type of the destruction of all the enemies of Christ and his kingdom.