Musannaf Ibn Abi Shayba 19:131

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, from Hisham ibn Urwah, from his father, regarding a man who accuses a group of people all together: He said: If it was in one statement, then there is one prescribed punishment (hadd). And if he separated them, then upon him is a prescribed punishment for each man among them. And the thief is like that.