Exodus 17
10 Ref So Joshua did as Moses had told him, and fought with Amalek; and Moses, Aaron, and Hur went up to the top of the hill.
11 Ref It happened, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed.
12 Ref But Moses' hands were heavy; and they took a stone, and put it under him, and he sat on it. Aaron and Hur held up his hands, the one on the one side, and the other on the other side. His hands were steady until sunset.