Exodus 17:8-13

Then Amalek came and fought with Israel in Rephidim. So Moses said to Joshua, “Choose men for us and go out, fight against Amalek. Tomorrow 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 against Amalek. And Moses, Aaron, and Hur went up to the top of the hill. Now when Moses held up his hand, Israel prevailed, but when he let down his hand, Amalek prevailed. But Moses’ hands became heavy. So they took a stone, and put it under him, and he sat on it. And Aaron and Hur supported his hands, one on one side, and the other on the other side. And his hands were steady until the going down of the sun. So Joshua laid low Amalek and his people with the edge of the sword.