Abu Hurairah (RAA) narrated that The Messenger of Allah (ﷺ) said:
"Otherwise he will be required to work to pay for his freedom, but he must not be overburdened." Agreed upon. (RU)
English reference (RU): Book 15, Hadith 1467 (RU)
Arabic reference (RU): Book 15, Hadith 1423 (RU)