Exodus 17:10-13

¹⁰Joshua did as Moses told him, and fought against Amalek; and Moses, Aaron, and Hur went up to the top of the hill. ¹¹So it came about when Moses held his hand up, that Israel prevailed, and when he let his hand down, Amalek prevailed. ¹²But Moses’ hands were heavy. Then 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 one on the other. Thus his hands were steady until the sun set. ¹³So Joshua overwhelmed Amalek and his people with the edge of the sword.