ENOfficial
It was narrated that Ibn Abbas said: “I would like the people to reduce (the will) from one third to one quarter, because the Messenger of Allah (ﷺ) said: 'One third is a lot.'”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ وَدِدْتُ أَنَّ النَّاسَ، غَضُّوا مِنَ الثُّلُثِ إِلَى الرُّبُعِ لأَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الثُّلُثُ كَبِيرٌ - أَوْ كَثِيرٌ - " .
sunnah.com