Exodus 17:11-14

11While Moses held up his hand, Israel prevailed, but whenever he put his hand down, Amalek prevailed.

12When Moses’s hands grew heavy, they took a stone and put it under him, and he sat down on it. Then Aaron and Hur supported his hands, one on one side and one on the other so that his hands remained steady until the sun went down.

13So Joshua defeated Amalek and his army with the sword.

14The Lord then said to Moses, “Write this down on a scroll as a reminder and recite it to Joshua: I will completely blot out the memory of Amalek under heaven.”