مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2075
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas said: I wish that the people would reduce one-third to one-quarter when making bequests, because the Prophet (ﷺ) said: "One third is a lot.”
Musnad Ahmad 2076Its isnad is saheeh, al-Bukhari (2743) and Muslim (1629)]