Awf bin al-Harith narrates from Sayyiduna Nawfal bin al-Mughirah (may Allah be pleased with him) that he said: I accepted Islam while I had five wives, so I asked the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Separate from one, and keep the other four." So I went to the oldest of them in my marriage, who had been barren for sixty years, and separated from her.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14057