The Messenger of Allah ﷺ said, "Whoever frees his share, however small, in a slave is responsible for completing the slave's freedom from his own wealth, if he has wealth. If he has no wealth, the slave is to be valued at a fair price, then the slave is to work to earn the value of the remaining shares for his other owner, without being burdened beyond his capacity."
حدثنا نصر بن علي أخبرنا يزيد يعني ابن زريع ح و حدثنا علي بن عبد الله حدثنا محمد بن بشر وهذا لفظه عن سعيد بن أبي عروبة عن قتادة عن النضر بن أنس عن بشير بن نهيك
عن رسول الله ﷺ قال من أعتق شقصا له أو شقيصا له في مملوك فخلاصه عليه في ماله إن كان له مال فإن لم يكن له مال قوم العبد قيمة عدل ثم استسعي لصاحبه في قيمته غير مشقوق عليه
Abu Dawud said regarding both of these hadiths, "He was then required to work for it without being placed under hardship," and this is the wording of Ali.Sourcing: Bukhari related it in the book of Emancipation, chapter "If someone frees his share in a slave but has no wealth... etc.," hadith 2527, from the hadith of Yazid bin Zuray. And Muslim related it in the book of Emancipation, chapter mentioning the slave working to earn his freedom, hadith 1503, from the hadith of Saeed bin Abu Aruba, with similar wording.