Musnad Ahmad 27:188

Isma'il narrated to us, Ayyub narrated to us, from Nafi', from Ibn 'Umar, from the Prophet (peace be upon him): "Whoever emancipates a portion—or he said: a share of his, or he said: a partnership of his—in a slave, and he possesses wealth that reaches his price according to a fair valuation, then he is emancipated. Otherwise, he is emancipated to the extent of what was emancipated of him." Ayyub said: "Nafi' would sometimes say this in this hadith and sometimes he would not say it, so I do not know if it is in the hadith, or if Nafi' said it from himself"—meaning his saying: "he is emancipated to the extent of what was emancipated of him."