Musannaf Ibn Abi Shayba 19:51

Abu Bakr narrated to us, he said: Yazid ibn Harun narrated to us, from Hammad ibn Salamah, from Humayd, that: Umar ibn Abd al-Aziz wrote regarding a thief: He is not to have his hand cut off until he exits the house with the property, perhaps he may repent before he exits the house.