Musnad Ahmad 27:578

Muhammad ibn Ja'far narrated to us, Mu'ammar narrated to us, Ibn Shihab and 'Abd al-A'la informed us, from Mu'ammar, from al-Zuhri, from Salim ibn 'Abd Allah, from 'Abd Allah ibn 'Umar, who said: Ghilan ibn Salamah accepted Islam while he had ten wives under him. The Messenger of Allah (peace and blessings of Allah be upon him) said to him: "Take four of them."