Abu Huraira reported Allah's Messenger (ﷺ) as saying: He who emancipates his portion in a slave, full emancipation may be secured for him out of his property (if he has money) if he has enough property to meet (the required expenses), but if he has not enough property, the slave should be put to extra labour (in order to earn money for buying his freedom), but he should not be overburdened.
Source: sunnah.com
Other translations
Arabic
وَحَدَّثَنِي عَمْرٌو النَّاقِدُ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ إِبْرَاهِيمَ، عَنِ ابْنِ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، عَنِ النَّضْرِ بْنِ أَنَسٍ، عَنْ بَشِيرِ بْنِ نَهِيكٍ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " مَنْ أَعْتَقَ شَقِيصًا لَهُ فِي عَبْدٍ فَخَلاَصُهُ فِي مَالِهِ إِنْ كَانَ لَهُ مَالٌ فَإِنْ لَمْ يَكُنْ لَهُ مَالٌ اسْتُسْعِيَ الْعَبْدُ غَيْرَ مَشْقُوقٍ عَلَيْهِ " .
sunnah.com