Hattip Carl Quintanilla. https://bsky.app/profile/carlquintanilla.bsky.social/post/3lrykqtmtu22l
Other goodies:
https://bsky.app/profile/carlquintanilla.bsky.social/post/3lrykxridh22l
https://bsky.app/profile/carlquintanilla.bsky.social/post/3lrykwlw5ps2l
https://bsky.app/profile/carlquintanilla.bsky.social/post/3lryknme2wc2l
…and as this is often misinterpreted, the kettle is shiny and clean so the pot sees its own reflection distorted and blames it on the reflector…
So the earliest we have of this kind of saying is from Don Quixote where it is about deflecting hypocritical criticism from the 1600s. The shiny kettle/black pot version is more recent one gaining prominence in the late 1800s.