What is the maximum extent a bequest to a non-heir is valid without the heirs' approval?

Primary text

A bequest made to a non-heir becomes binding concerning one-third (al-thuluth) of the estate without requiring the approval of the heirs. Any portion exceeding one-third is suspended pending their ratification. If the heirs approve the excess, it is enforced; if they reject it, it becomes void. This is the position of all scholars. The evidence for this is the Prophet's command to Saad to only bequeath one-third, stating, 'The third is much.' Further evidence is the narration regarding Imran ibn Husayn's case concerning his slaves, where the Prophet divided them into three parts, indicating that disposition beyond one-third is not valid without heir approval because the right belongs to them.