War with Amalek

Ex 17:8: Then came Amalek, and fought with Israel in Rephidim.
Ex 17:9: And Moses said unto Joshua, Choose us out men, and go out, fight with Amalek: to morrow I will stand on the top of the hill with the rod of God in mine hand.
Ex 17:10: So Joshua did as Moses had said to him, and fought with Amalek: and Moses, Aaron, and Hur went up to the top of the hill.
Ex 17:11: And it came to pass, when Moses held up his hand, that Israel prevailed: and when he let down his hand, Amalek prevailed.
Ex 17:12: But Moses' hands were heavy; and they took a stone, and put it under him, and he sat thereon; and Aaron and Hur stayed up his hands, the one on the one side, and the other on the other side; and his hands were steady until the going down of the sun.
Ex 17:13: And Joshua discomfited Amalek and his people with the edge of the sword.
Ex 17:14: And the LORD said unto Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua: for I will utterly put out the remembrance of Amalek from under heaven.
Ex 17:15: And Moses built an altar, and called the name of it Jehovah-nissi:
Ex 17:16: For he said, Because the LORD hath sworn that the LORD will have war with Amalek from generation to generation.