Uthman bin Muhammad bin Abi Suwayd (may Allah have mercy on him) said that the Messenger of Allah (peace and blessings be upon him) said to Ghaylan bin Salamah al-Thaqafi (may Allah be pleased with him), when he accepted Islam while he had ten wives: "Choose four, and divorce all the rest."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14047