Exodus 17:14-16
14 Then the Lord said to Moses, “Write this as a memorial in a book and recite it in the ears of Joshua, that I will utterly blot out the memory of Amalek from under heaven.” 15 And Moses built an altar and called the name of it, The Lord Is My Banner, 16 saying, “A hand upon the throne of the Lord! The Lord will have war with Amalek from generation to generation.”