Exodus 17
9 Ref And Moses said to Joshua, Get together a band of men for us and go out, make war on Amalek: tomorrow I will take my place on the top of the hill with the rod of God in my hand.
10 Ref So Joshua did as Moses said to him, and went to war with Amalek: and Moses, Aaron, and Hur went up to the top of the hill.
11 Ref Now while Moses' hand was lifted up, Israel was the stronger: but when he let his hand go down, Amalek became the stronger.
12 Ref But Moses' hands became tired; so they put a stone under him and he took his seat on it, Aaron and Hur supporting his hands, one on one side and one on the other; so his hands were kept up without falling till the sun went down.
13 Ref And Joshua overcame Amalek and his people with the sword.