Sahih Muslim 11479
In-book no 4202وَحَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، بِهَذَا الإِسْنَادِ قَالَ " مَنْ أَعْتَقَ شَقِيصًا مِنْ مَمْلُوكٍ فَهُوَ حُرٌّ مِنْ مَالِهِ " .
This hadith has been narrated on the authority of Shu'ba with the same chain of transmitters (and the words are): " He who emancipates a portion in a slave, he should (secure full) freedom for him from his property."