⁸ Now Amalek came and fought with Israel in Rephidim. ⁹ And Moses said to Joshua, “Choose us some 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 said to him, and fought with Amalek. And Moses, Aaron, and Hur went up to the top of the hill. ¹¹ And so it was, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed. 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. ¹³ So Joshua defeated Amalek and his people with the edge of the sword.

¹⁴ Then the Lord said to Moses, “Write this for a memorial in the book and recount it in the hearing of Joshua, that I will utterly blot out the remembrance of Amalek from under heaven.” ¹⁵ And Moses built an altar and called its name, The-Lord-Is-My-Banner;

Exodus 17:8-15