Exodus 17:11-14

11So it came about when Moses held his hand up, that Israel prevailed, and when he let his hand 1down, Amalek prevailed. 12But Moses’ hands were heavy. Then they took a stone and put it under him, and he sat on it; and Aaron and Hur 2supported his hands, one on one side and one on the other. Thus his hands were steady until the sun set. 13So Joshua 3overwhelmed Amalek and his people with the edge of the sword.

14Then the Lord said to Moses, “4Write this in 5a book as a memorial and 6recite it to Joshua, 7that 8I will utterly blot out the memory of Amalek from under heaven.”