Exodus 17:14, 16

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]

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