Israel defeats Amalek
In a battle with the Amalekites, the Israelites won as long as Moses held up his hands. The Israelites won and Moses built an altar.
Key passages
Ex 17:8–16

And Amalek came and fought with Israel at Rephidim. And Moses said to Joshua, “Choose men for us, and go out, fight against Amalek tomorrow. I will be standing on the top of the hill, and the staff of God will be in my hand.” And Joshua did as Moses had said to him …