Exodus 17:14-16

14Then 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.”

15And Moses built an altar and named it The Lord Is My Banner;

16saying, “The Lord has sworn [an oath]; the Lord will have war against [the people of] Amalek from generation to generation.”