Exodus 17:8-16 - Battle With The Amalekites
8 Then Amalek came, and fought with Israel in Rephidim. 9 And Moses said to Joshua, Choose us out men, and go out, fight with Amalek. Tomorrow I will stand on the top of the hill with the rod of God in my hand.
10 So Joshua did as Moses had said to him, and fought with Amalek. And Moses, Aaron, and Hur went up to the top of the hill. 11 And it came to pass, when Moses held up his hand, that Israel prevailed, and when he let down his hand, Amalek prevailed. 12 But Moses' hands were heavy. And they took a stone, and put it under him, and he sat on it. and Aaron and Hur held up his hands, the one on the one side, and the other on the other side. And his hands were steady until the going do 13 And Joshua weakened Amalek and his people with the edge of the sword.
14 And LORD said to Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua: that I will utterly blot out the remembrance of Amalek from under heaven.
15 And Moses built an altar, and called the name of it LORD-nissi. 16 And he said, LORD has sworn, LORD will have war with Amalek from generation to generation.