Exodus 17:12-13

King James Version

¹² But Moses hands were heavy; and they took a stone, and put it under him, and he sat thereon; and Aaron and Hur stayed up his hands, the one on the one side, and the other on the other side; and his hands were steady until the going down of the sun.

¹³ And Joshua discomfited Amalek and his people with the edge of the sword.