It is dislike to look down upon a slave
حَدَّثَنَا أَبُو النُّعْمَانِ، حَدَّثَنَا جَرِيرُ بْنُ حَازِمٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " مَنْ أَعْتَقَ نَصِيبًا لَهُ مِنَ الْعَبْدِ، فَكَانَ لَهُ مِنَ الْمَالِ مَا يَبْلُغُ قِيمَتَهُ، يُقَوَّمُ عَلَيْهِ قِيمَةَ عَدْلٍ، وَأُعْتِقَ مِنْ مَالِهِ، وَإِلاَّ فَقَدْ عَتَقَ مِنْهُ ".
Narrated Ibn `Umar: The Prophet (ﷺ) said, "If one manumits his share of a common slave (Abd), and he has money sufficient to free the remaining portion of the price of the slave (justly estimated), then he should free the slave completely by paying the rest of his price; otherwise the slave is freed partly. "