It was narrated from Ibn`Umar that the Messenger of Allah (ﷺ) said:
"Whoever frees a slave who has some wealth, the slave's wealth belongs to him, unless the master stipulates that it will belong to him." (RU)
English reference (RU): Vol. 3, Book 19, Hadith 2529 (RU)
Arabic reference (RU): Book 19, Hadith 2625 (RU)