Ibn 'Umar (RAA) narrated that The Messenger of Allah (ﷺ) said:
"The Wala' (of a manumitted slave) is considered as one's lineage, not to be sold or donated (refer to hadith no. 984)." Related by Ash-Shafi'i. Ibn Hibban and Al-Hakim graded it as Sahih. It is also related by Al-Bukhari and Muslim with different wording
English reference: Book 15, Hadith 1473
Arabic reference: Book 15, Hadith 1429