дай ему палец, он и всю руку откусит

• ДАЙ ЕМУ ПАЛЕЦ, ОН И ВСЮ РУКУ ОТКУСИТ

[saying]

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⇒ if you make a small concession to or do a favor for him (her etc), he (she etc) will demand even more:

- ≈ give him <her etc> an inch and he'll <she'll etc> take a mile;

- given an inch he'll <she'll etc> take a yard;

- give <offer> him <her etc> a finger and he'll <she'll etc> grab your whole arm.

     ♦ [author's usage] [Захар:] Народ наш груб, он некультурен... и, если протянуть ему палец, он хватает всю руку... (Горький 1). [Zakhar:] Our people are coarse and uncultivated. If you offer them a finger they'll grab your whole arm (1b).