Exodus 17:14-17:16
Then the Lord said to Moses, "Inscribe this in a document as a reminder, and read it aloud to Joshua: I will utterly blot out the memory of Amalek from under heaven!" 15 And Moses built an altar and named it Adonai-nissi.
He said, "It means, 'Hand upon the throne of the Lord!' The Lord will be at war with Amalek throughout the ages."