Humaydah bin al-Shamardal narrates from Sayyiduna al-Harith bin Qays (may Allah be pleased with him) that al-Harith (may Allah be pleased with him) said: I and my 8 wives accepted Islam, and I mentioned this before the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) said: "Choose four of them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14052