The Messenger of Allah ﷺ forbade the sale of the right of wala and its gift.
أن رسول الله ﷺ نهي عن بيع الولاء، وعن هبته.
Malik related it in "Manumission and Patronage" (20) from Abdullah bin Dinar, from Abdullah bin Umar, as mentioned. Bukhari related it in "Manumission" (2535) via the route of Shubah, and Muslim in "Manumission" (1506) via the route of Sulayman bin Bilal and others, all of them from Abdullah bin Dinar with this wording. Muslim said, "All people are dependent on Abdullah bin Dinar for this hadith."Tirmidhi (2126) said, "This is a hasan sahih hadith. We do not know it except through the hadith of Abdullah bin Dinar, from Ibn Umar... Shubah, Sufyan Thawri, and Malik bin Anas have related it from Abdullah bin Dinar. It is reported that Shubah said, 'I wished that when Abdullah bin Dinar narrated this hadith he would have permitted me to rise to him and kiss his head.'"Abu Isa said, "Yahya bin Salim related this hadith from Ubaydullah bin Umar, from Nafi, from Ibn Umar, from the Prophet ﷺ, and this is a mistake. Yahya bin Salim erred in it. The correct version is from Ubaydullah bin Umar, from Abdullah bin Dinar, from Ibn Umar, from the Prophet ﷺ. This is how more than one narrator has related it, from Ubaydullah bin Umar." End of quote.