Musannaf Ibn Abi Shayba 13:3422

Abu Bakr narrated to us, he said: Isma'il ibn 'Ulayyah narrated to us, from Ayyub, from Abu Qilabah, from Abu al-Muhallab, from 'Imran ibn Husayn: That a man had six slaves, and he emancipated them at the time of his death. The Prophet, may Allah bless him and grant him peace, drew lots between them, so he emancipated two of them and kept four in slavery.