не учи ученого

• НЕ УЧИ УЧЕНОГО coll

[Imper sent; occas. used without negation to convey the same meaning; fixed WO]

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⇒ do not give advice to those who are more experienced at sth. than you are:

- an old fox needs not (doesn't need) to be taught tricks;

- don't (try to) teach your grandmother to suck eggs.

     ♦ "Неплохо, - сказал Антон, прочитав моё сочинение. - Только вот тебе мой совет: ...в Главлит дай липу, а не подлинник... Иначе не пропустят. И на конгресс не поедешь". - "Само собой разумеется, - сказал я, возбуждённый удачей. - Не учи учёного" (Зиновьев 2). That's not bad," said Anton when he'd read the work. "But here's my advice: don't give the real thing to the censorship; give them a bit of window-dressing. ...Otherwise they'll never pass it, and you'll never make it to the Congress." "But of course!" I said elated by my success. "Don't teach your grandmother to suck eggs!" (2a).