Musannaf Ibn Abi Shayba 35:238

Ibn ‘Uyaynah and Marwan ibn Mu’awiyah narrated to us, from Ma’mar, from al-Zuhri, from Salim, from Ibn ‘Umar, that Ghaylan ibn Salamah accepted Islam while he had eight wives. The Prophet, peace and blessings of Allah be upon him, ordered him to choose four of them. And it was mentioned that Abu Hanifah said: "The first four."