。
You can't give what you don't have.
Literal
Not-exist sleeve [topic-は] shake-not.
無い袖は振れぬ is a ことわざ — literally 'you can't shake sleeves you don't have.' In old Japan, sleeves held money and small goods, so 'shaking your sleeves' meant offering or giving. The saying means 'you can't give what you don't have.' 振れぬ uses classical negative ぬ.