Musannaf Ibn Abi Shayba 35:39

Ibn ‘Uyaynah narrated to us, from al-Zuhri, from ‘Ubayd Allah ibn ‘Abd Allah, from Zayd ibn Khalid, Shibl, and Abu Hurayrah, who said: We were with the Prophet, may Allah bless him and grant him peace, when a man came to him and asked him about a slave woman who commits adultery before she is married. He said: "Flog her. If she repeats it, then flog her." He said: "On the third or fourth time, sell her, even if for a rope of hair."