Exodus 17:11-16

17:11 Whenever Moses would raise his hands, then Israel prevailed, but whenever he would rest his hands, then Amalek prevailed. 17:12 When the hands of Moses became heavy, they took a stone and put it under him, and Aaron and Hur held up his hands, one on one side and one on the other, and so his hands were steady until the sun went down. 17:13 So Joshua destroyed Amalek and his army with the sword.

17:14 The Lord said to Moses, “Write this as a memorial in the book, and rehearse it in Joshua’s hearing; for I will surely wipe out the remembrance of Amalek from under heaven. 17:15 Moses built an altar, and he called it “The Lord is my Banner,” 17:16 for he said, “For a hand was lifted up to the throne of the Lord – that the Lord will have war with Amalek from generation to generation.”