The act represents the efficacy of intercessory prayer—offered undoubtedly by Moses—a point of great importance to the Israelites at that time and …

When Moses held up his hand ... Israel prevailed, etc. — In order to teach the lesson of the value of intercessory prayer…

And it came to pass, when Moses held up his hand, that Israel
prevailed
With his rod …

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.…