Jami` at-Tirmidhi 2100
Qabisah bin Dhuw'aib said:
"A grandmother - the mother of a mother, or the mother of a father - came to Abu Bakr and she said: 'a son of my son' - or, 'a son of my daughter died, and I have been informed that there is a right ( from the wealth) for me in the Book.' So Abu Bakr said: 'I do not find that there is a right for you in the Book, and I have not heard that the Messenger of Allah(S.A.W) judged anything for you. I shall ask the people.' So, Al-Mughirah bin Shu'bah testified that the Messenger of Allah(S.A.W) gave her (case) a sixth. He said: 'And who heard that along with you?' He said: 'Muhammad bin Maslamah.'" He said: "So he gave her a sixth. Then the other grandmother who was left behind came to 'Umar." Sufyan said: "And  Ma'mar said to me in addition, from Az-Zuhri - and I do not remember it to be from Az-Zuhri, rather I remember it to be from Ma'mar - that 'Umar said: 'If the two of you are together then it is for both of you, and whichever of you is alone with it (the sixth), then it is for her.'"
حَدَّثَنَا ابْنُ أَبِي عُمَرَ، قال حَدَّثَنَا سُفْيَانُ، قال حَدَّثَنَا الزُّهْرِيُّ، قَالَ مَرَّةً قَالَ قَبِيصَةُ وَقَالَ مَرَّةً رَجُلٌ عَنْ قَبِيصَةَ بْنِ ذُؤَيْبٍ قَالَ جَاءَتِ الْجَدَّةُ أُمُّ الأُمِّ أَوْ أُمُّ الأَبِ إِلَى أَبِي بَكْرٍ فَقَالَتْ إِنَّ ابْنَ ابْنِي أَوِ ابْنَ بِنْتِي مَاتَ وَقَدْ أُخْبِرْتُ أَنَّ لِي فِي كِتَابِ اللَّهِ حَقًّا ‏.‏ فَقَالَ أَبُو بَكْرٍ مَا أَجِدُ لَكِ فِي الْكِتَابِ مِنْ حَقٍّ وَمَا سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم قَضَى لَكِ بِشَيْءٍ وَسَأَسْأَلُ النَّاسَ ‏.‏ قَالَ فَسَأَلَ فَشَهِدَ الْمُغِيرَةُ بْنُ شُعْبَةَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَعْطَاهَا السُّدُسَ ‏.‏ قَالَ وَمَنْ سَمِعَ ذَلِكَ مَعَكَ قَالَ مُحَمَّدُ بْنُ مَسْلَمَةَ ‏.‏ قَالَ فَأَعْطَاهَا السُّدُسَ ثُمَّ جَاءَتِ الْجَدَّةُ الأُخْرَى الَّتِي تُخَالِفُهَا إِلَى عُمَرَ ‏.‏ قَالَ سُفْيَانُ وَزَادَنِي فِيهِ مَعْمَرٌ عَنِ الزُّهْرِيِّ وَلَمْ أَحْفَظْهُ عَنِ الزُّهْرِيِّ وَلَكِنْ حَفِظْتُهُ مِنْ مَعْمَرٍ أَنَّ عُمَرَ قَالَ إِنِ اجْتَمَعْتُمَا فَهُوَ لَكُمَا وَأَيَّتُكُمَا انْفَرَدَتْ بِهِ فَهُوَ لَهَا ‏.‏