Musnad Ahmad 27:1819

Ibn Numayr and Muhammad ibn ‘Ubayd narrated to us, they said: ‘Ubayd Allah narrated to us, from Nafi‘, from Ibn ‘Umar, from the Messenger of Allah (may Allah bless him and grant him peace), who said: "Whoever emancipates his share in a slave, he is responsible for emancipating the whole of him. If he has wealth that reaches his price, he shall be appraised [against him] at a fair valuation. If he does not have wealth, then only that part of him which was emancipated is emancipated."