What is the preferable maximum limit for a bequest (Wasiyyah), even for a wealthy person?

Primary text

It is preferable not to bequeath the entire one-third (al-Thuluth) of one's estate, even if wealthy, because the Prophet (peace be upon him) stated, "The one-third is a large amount." This position is supported by Ibn Abbas, who stated that people should reduce the bequest below one-third based on the Prophet's statement. The primary evidence is the incident where the Prophet instructed Sa'd ibn Abi Waqqas to reduce his bequest from all of his wealth down to one-tenth, eventually agreeing upon one-third, while clarifying that even one-third is excessive. Following this principle, the best course for a wealthy person is to bequeath one-fifth (al-Khums). This view is narrated regarding Abu Bakr Al-Siddiq and Ali ibn Abi Talib, and it represents the apparent position of the Salaf (early generations) and the scholars of Basra.