Musannaf Ibn Abi Shayba 9:1281

Bakr ibn Abd al-Rahman narrated to us, he said: Isa ibn al-Mukhtar narrated to us, from Ibn Abi Layla, from Humaydah ibn al-Shamardal, from Qays ibn al-Harith al-Asadi, that he embraced Islam while he had eight wives, so the Messenger of Allah, peace and blessings of Allah be upon him, ordered him to choose four of them.