Shemot 17:10-12

Orthodox Jewish Bible

¹⁰ So Yehoshua did as Moshe had said to him, and did battle with Amalek; and Moshe, Aharon, and Chur went up to the top of the hill.

¹¹ And it came to pass, as long as Moshe held up his yad, that Yisroel prevailed; and when he let down his yad, Amalek prevailed.

¹² When the hands of Moshe grew heavy, they took an even (stone), and put it under him, and he sat thereon; and Aharon and Chur supported his hands, the one on the one side, and the other on the other side; and his hands held emunah (steady) until bo hashemesh (sunset).