´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.'"
Hadith ReferenceSunan an-Nasa'i / The Book of Wills / Hadith: 3664
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه