And so it was, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed.
Exodus 17:11
Surrounding context
17:10 So Joshua did as Moses said to him, and fought with Amalek. And Moses, Aaron, and Hur went up to the top of the hill.
17:11 And so it was, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed.
17:12 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.