Exodus 17:14-16

Then the LORD said to Moses, “Write this on a scroll as something to be remembered and make sure that Joshua hears it, because I will completely blot out the name of Amalek from under heaven.” Moses built an altar and called it The LORD is my Banner. He said, “Because hands were lifted up against the throne of the LORD, the LORD will be at war against the Amalekites from generation to generation.”