Musannaf Ibn Abi Shayba 35:43

Mu'alla ibn Mansur narrated to us, from Abu Uways, from Abdullah ibn Abi Bakr, from Abbad ibn Tamim, from his paternal uncle—and he was a Badr-warrior—who said: The Prophet, peace and blessings of Allah be upon him, said: "If the slave-woman commits adultery, then flog her. Then if she commits adultery, then flog her. Then if she commits adultery, then flog her. Then sell her, even if for a rope." And he mentioned that Abu Hanifa said: Her master shall not flog her.