Musannaf Ibn Abi Shayba 13:2856

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Ayyub, from Humayd ibn Hilal, from Hakim ibn ‘Iqal, who said: Uthman wrote to my father: "Purchase one hundred people of a household, and do not separate between a parent and their child."