Can an heir revoke their authorization of a bequest exceeding one-third if they later claim the estate value was underestimated?

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If an heir authorizes a bequest exceeding the one-third limit, claiming ignorance of the estate's true, greater value, their authorization is generally upheld if the testator (the one making the bequest) has evidence proving the heir knew the extent of the estate, or if the estate value was apparent and known. In such cases, the heir's claim of ignorance is not accepted, unless the view is taken that the authorization constitutes a new gift (*hibah*), in which case revocation is permissible as it would be in a similar gift. If no evidence of the heir's prior knowledge exists, the heir's statement, accompanied by an oath, is accepted. This is because the authorization is treated as a release (*ibra'*) which is invalid when based on an unknown quantity. The principle of lack of knowledge prevails, thus accepting the heir's statement upon oath.