Musannaf Ibn Abi Shayba 13:3178

Abu Bakr narrated to us, he said: Mu'tamir narrated to us, from Humayd al-Tawil, from Iyas ibn Mu'awiyah: He was asked about a slave owned by three people, where one of them made a contract of manumission (kitabah) for his share, and one of them emancipated his share. Then the slave died and left behind wealth. Al-Hasan and Iyas judged that whatever he left behind is to be divided among them equally.