It is narrated from al-Hasan (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: "Wala' is a bond (of flesh) like the bond of lineage; it is neither sold nor given away as a gift."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12381