Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: Ghaylan bin Salamah al-Thaqafi accepted Islam while he had ten wives, and the Messenger of Allah (peace and blessings be upon him) commanded him to keep four and leave the rest. The narrator said: Safwan bin Umayyah accepted Islam while he had 8 wives, and he (peace and blessings be upon him) said: "Keep four and separate from the rest."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14050