Musnad Ahmad 30:1445

'Affan narrated to us, Hammam narrated to us, Qatadah narrated to us, from An-Nadr ibn Anas, from Bashir ibn Nahik, from Abu Hurairah, that a man emancipated a portion of a slave, and the Prophet, peace and blessings of Allah be upon him, permitted his emancipation and made him liable for the remainder of his price.