Exo 17:8 Then Amalek came and fought with Israel at Rephidim. So Moses said to Joshua, “Choose for us men, and go out and fight with Amalek. Tomorrow I will stand on the top of the hill with the staff of God in my hand.” So Joshua did as Moses told him, and fought with Amalek, while Moses, Aaron, and Hur went up to the top of the hill. Whenever Moses held up his hand, Israel prevailed, and whenever he lowered his hand, Amalek prevailed. But Moses’ hands grew weary, so they took a stone and put it under him, and he sat on it, while Aaron and Hur held up his hands, one on one side, and the other on the other side. So his hands were steady until the going down of the sun. And Joshua overwhelmed Amalek and his people with the sword. Then the LORD said to Moses, “Write this as a memorial in a book and recite it in the ears of Joshua, that I will utterly blot out the memory of Amalek from under heaven.” And Moses built an altar and called the name of it, The LORD Is My Banner, saying, “A hand upon the throne of the LORD! The LORD will have war with Amalek from generation to generation.”
Deuteronomy 25:17 “Remember what Amalek did to you on the way as you came out of Egypt,
1 Samuel 15:2 Thus says the LORD of hosts, ‘I have noted what Amalek did to Israel in opposing them on the way when they came up out of Egypt.
The Amalek’s present hostility was not altogether unprovoked. No doubt they regarded the Sinaitic region as their own, and as the most valuable portion of their territory, since it contained their summer and autumn pastures. During their absence in its more northern portion, where there was pasture for their flocks after the spring rains, a swarm of emigrants had occupied some of their best lands, and threatened to seize the remainder. Naturally, they would resent the occupation. They would not understand that it was only temporary. They would regard the Israelites as intruders, robbers, persons entitled to scant favour at their hands. Accordingly, they swooped upon them without mercy, attacked their rear as they were upon the march, cut off their stragglers, and slew many that were “feeble, faint, and weary” (Deuteronomy 25:17-18). Remember what Amalek did to you on the way as you were coming out of Egypt, 18 “how he met you on the way and attacked your rear ranks, all the stragglers at your rear, when you [were] tired and weary; and he did not fear God.They then encamped in their neighbourhood, with the design of renewing the struggle on the next day. It was under these circumstances that Moses had to make his arrangements. (Ellicott)
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. (Henry)
The Amalekites were at that time the most powerful race in the Peninsula; here they took their position as the chief of the pagans. They were also the first among the pagans who attacked God’s people, and as such were marked out for punishment and destruction. (Barnes)
This is the first passage that mentions Joshua. We find him doing what he did until the time Moses passed from the scene – Joshua served the LORD and Moses faithfully.
This amazing passage shows us that life or death for Israel depended on the prayers of one man. Moses prayed as we should pray – with passion, believing that life and death – perhaps eternally – depended on prayer. It can be difficult to reconcile this with knowing God has a pre-ordained plan. But God didn’t want Moses to concern himself with that – he was to pray as if it really mattered. Just because we can’t figure out how our prayers mesh with God’s pre-ordained plan never means we should stop believing that prayer matters. Prayer is sometimes sweet and easy; other times it is hard work. This is why Paul described the ministry of Epaphras as always laboring fervently for you in prayers (Colossians 4:12), and why Paul wrote we must continue earnestly in prayer, being vigilant in it with thanksgiving (Colossians 4:2). Though this was Moses’ work to do, it was more than he could do by himself. Moses alone could not win the battle of prayer. He needed others to come by his side and strengthen him in prayer. This amazing passage shows us the great importance of prayer. Life and death – the course of history itself – depended upon prayer. We can conclude that many times the people of God are defeated today because they will not pray, or prayer does not support their work. (Guzik)
Nevertheless, Joshua had to fight. Praying Moses did not eliminate what Joshua had to do. The battle was won with prayer, but also through normal instruments – the work of the army, led by Joshua. “Prayer is a downright mockery if it does not lead us into the practical use of means likely to promote the ends for which we pray.” (Spurgeon)