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." (IT)
English reference (IT): Vol. 3, Book 19, Hadith 2529 (IT)
Arabic reference (IT): Book 19, Hadith 2625 (IT)