"I heard 'Urwah bin Az-Zubair say: "Aishah used to narrate that he Prophet of Allah said: The hand (of the thief) should not be cut off except for a shield or its equivalent in value. And he said that 'Urwah said: A shield is (worth) four Dirhams. And he (the narrator) said: I heard sulaiman bin Yasar say that he heard 'Amrah say: I heard 'Aishah narrate that she heard the Messenger of Allah say: The hand (of the thief) should not be cut off except for four Dinars or more."
Sunan an-Nasa'i Book 46, Hadith 69