Exodus 17:10-12

Amplified Bible

¹⁰ So Joshua did as Moses said, and fought with Amalek; and Moses, Aaron, and ^[a]Hur went up to the hilltop. ¹¹ Now when Moses held up his hand, Israel prevailed, and when he lowered his hand [due to fatigue], Amalek prevailed. ¹² But Moses’ hands were heavy and he grew tired. So they took a stone and put it under him, and he sat on it. Then Aaron and Hur held up his hands, one on one side and one on the other side; so it was that his hands were steady until the sun set.