Yahya related to me from Malik from Ibn Shihab from Uthman ibnIshaq ibn Kharasha that Qabisa ibn Dhu'ayb said, "A grandmother cameto Abu Bakr as-Siddiq and asked him for her inheritance. Abu Bakr saidto her, 'You have nothing in the Book of Allah, and I do not know thatyou have anything in the sunna of the Messenger of Allah, may Allahbless him and grant him peace. Go away therefore, until I havequestioned the people.' (i.e.the Companions). He questioned thepeople, and al-Mughira ibn Shuba said, 'I was present with theMessenger of Allah, may Allah bless him and grant him peace, when hegave the grandmother a sixth.' Abu Bakr said, 'Was there anybody elsewith you?' Muhammad ibn Maslama al-Ansari stood up and said the likeof what al-Mughira said. Abu Bakr as-Siddiq gave it to her. Then theother grandmother came to Umar ibn al-Khattab and asked him for herinheritance. He said to her, "You have nothing in the Book of Allah,and what has been decided is only for other than you, and I am not oneto add to the fixed shares, other than that sixth. If there are two ofyou together, it is between you. If eitherof you is left alone withit, it is hers."
USC-MSA web (English) reference: Book 27, Hadith 4
Arabic reference: Book 27, Hadith 1080