Musannaf Ibn Abi Shayba 13:1768

Abu Bakr narrated to us, he said: Abu Usama and Ibn Numayr narrated to us, from Ubayd Allah, from Nafi’, from Ibn Umar, who said: The Prophet (peace and blessings of Allah be upon him) said: "If he is wealthy, he is liable (for the value of the slave), and if he is in difficulty, he emancipates from him what he has emancipated."