Wikipedia:Articles for deletion/Teaching grandmother to suck eggs
While there exist sources confirming the ''existence'' of this phrase, by no means does this amount to significant coverage, and I don't see anything that would let us add content to this page beyond what a Wiktionary article would cover. Yes, there is a whole category for English idioms-- but those pages are full of things like the history of its usage, its use in notable media and pop culture, references in literature, political context, etc. (See Mexican standoff, Wolf in sheep's clothing, and Crocodile tears for some good examples.) I don't think that there exists information (yet) that would let this article be expanded enough to be worth having (per 
— User:Gilded, 04:00, 12 February 2019 (UTC)
Stance: delete
Cited policy: WP:WORDISSUBJECT (Wikipedia:Wikipedia is not a dictionary)