It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that a man came to the Prophet (peace and blessings be upon him) and said: My son's son has died; what share do I have of his inheritance? He (peace and blessings be upon him) said: "You have one sixth." When he turned to leave, he (peace and blessings be upon him) called him back and said: "The other sixth is also a grant (tu'mah) for you."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15386