Ibn Abbas said, "If only people would reduce from a third to a quarter, for the Messenger of Allah ﷺ said, 'A third is plenty.'"
حدثني ابن نمير حدثنا هشام عن أبيه
لو أن الناس غضوا من الثلث إلى الربع فإن رسول الله ﷺ قال الثلث كثير
Its isnad is sahih. Hisham is Ibn Urwa bin Zubayr. This hadith was also narrated by Bukhari and Muslim, as noted in Muntaqa 3276. What Ibn Abbas means by this is the bequest, since the statement of the Messenger of Allah ﷺ to Saad bin Abu Waqqas, "A third is a lot," indicates that it is better to bequeath less than a third. See 1099.