Wiktionary
pearl of wisdom
n. (context idiomatic often sarcasm sarcastic English) A succinct, insightful saying, piece of advice, or moral precept.
Usage examples of "pearl of wisdom".
Jones had reason to recall that pearl of wisdom as he listened to MacArthur in the old sandstone bank building that housed the HQ of the Southwest Pacific Area Command.
I wish there were some advice, even one lousy little pearl of wisdom, that I could hand down to you, but -- It's not for lack of trying, Duddel.