Musnad Abu Ya'la al-Mawsili 205:1

Ahmad ibn Ibrahim narrated to us, Hushaym narrated to us, from Ibn Abi Layla, from Humaydah ibn al-Shamardal, from Qays ibn al-Harith, who said: I embraced Islam while I had eight wives. I came to the Prophet, peace and blessings of Allah be upon him, and told him that. He said: "Choose four from among them."