أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ لَوْ غَضَّ النَّاسُ إِلَى الرُّبُعِ لأَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الثُّلُثَ وَالثُّلُثُ كَثِيرٌ أَوْ كَبِيرٌ ".
It was narrated that Ibn 'Abbas said: "If the people were to reduce (their bequests) to one-quarter (of their wealth, that would be better), because the Messenger of Allah said: 'One-third, and one-third is much or large.'" Translation Not Available
Book Ref: Sunan An Nisai Book 30 Hadith 3634
Web Ref: Sunan An Nisai Vol 4 Book 30 Hadith 3664