Exodus 17:13-15

So Joshua overwhelmed and defeated Amalek and his people with the edge of the sword. Then the LORD said to Moses, “Write this in the book as a memorial and recite it to Joshua, that I will utterly wipe out the memory of Amalek [and his people] from under heaven.” [1 Sam 15:2-8] And Moses built an altar and named it The LORD Is My Banner