Musannaf Ibn Abi Shayba 18:509

Abu Bakr narrated to us, he said: Hushaym and Ibn ‘Ulayyah narrated to us, from Khalid, from Ibn Sirin, from Shurayh, regarding a slave who wounded a free man. He said: If he wishes, he may exact retribution from him, and if he wishes, he may take from his master the blood money (arsh).