Exodus 17:14-16

Then the LORD said to Moses, “Write this for a memorial in the book and recount it in the hearing of Joshua, that I will utterly blot out the remembrance of Amalek from under heaven.” And Moses built an altar and called its name, The-LORD-Is-My-Banner; for he said, “Because the LORD has sworn: the LORD will have war with Amalek from generation to generation.”