Musannaf Ibn Abi Shayba 13:2589

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Isra’il, from ‘Abd al-‘Aziz ibn Rufay’, from Abu Bakr ibn ‘Amr ibn Hazm, that a man made a *kitabah* (contract of manumission) with a slave of his, and he set it for him in installments. He (the slave) came to him with all of his *kitabah* (payment), but the master refused to accept it except in installments. So the *mukātab* (the slave under contract) came to ‘Umar. ‘Umar sent for his master, and he came. He (the master) presented the money to him, but he (the master) refused to take it. ‘Umar said: "O Yarfa’, put it into the public treasury (Bayt al-Mal)." And he said to the master: "Take it in installments." And he said to the *mukātab*: "Go wherever you wish."