Sahih al-Bukhari 2743

Qutayba ibn Saʿid narrated to us; Sufyan narrated to us, from Hisham ibn ʿUrwa, from his father, from Ibn ʿAbbas (may Allah be pleased with them both), who said: I would advise people to reduce their bequests to a fourth, because the Messenger of Allah said, “A third, and a third is much”—or “great.”