Exodus 17:12-14

But Moses’ hands grew weary, so they took a stone and put it under him, and he sat on it, while Aaron and Hur held up his hands, one on one side, and the other on the other side. So his hands were steady until the going down of the sun. And Joshua overwhelmed Amalek and his people with the sword. Then the LORD said to Moses, “Write this as a memorial in a book and recite it in the ears of Joshua, that I will utterly blot out the memory of Amalek from under heaven.”