bite the hand that feeds one

bite the hand that feeds one (to turn against a benefactor, a friend or a supporter; to repay support with wrong) — отплатить кому-л. чёрной неблагодарностью || ≅ рубить сук, на котором сидишь {досл. кусать руку, которая кормит}

Example: Don't bite the hand that feeds you. You may need that hand one day. (urbandictionary.com)

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