Sunan Ibn Majah, Volume 4, Book 23, Hadith 2722 (DarusSalam) ⓘ
It was narrated that Ma’qil bin Yasar Al-Muzani said: “I heard the Prophet when a case was brought to him which involved the share of a grandfather. He gave him one third, or one sixth.”
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا شَبَابَةُ، حَدَّثَنَا يُونُسُ بْنُ أَبِي إِسْحَاقَ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَمْرِو بْنِ مَيْمُونٍ، عَنْ مَعْقِلِ بْنِ يَسَارٍ الْمُزَنِيِّ، قَالَ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم أُتِيَ بِفَرِيضَةٍ فِيهَا جَدٌّ فَأَعْطَاهُ ثُلُثًا أَوْ سُدُسًا .
also referenced under: Hadith 2722 (Reference) & Book 23, Hadith 2826 (In-Book)