Mujahid narrates from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The bond of wala' stands in the place of the bond of lineage; it cannot be sold or given as a gift. I will keep it where Allah has kept it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21442