The claim only 1/3 of the estates can be written in a will is a falsehood as the principle is rooted in an incident recorded in the authentic Hadith collections of Sahih al-Bukhari and Sahih Muslim.
It comes from the companion Sa’d ibn Abi Waqqas, who became severely ill and asked the Prophet Muhammad ﷺ if he could give away most of his wealth in charity. The specific dialogue from the Hadith is as follows:
Sa’d asked: “I want to will my property… Shall I give two-thirds of my property in charity?” The Prophet said, “No.”
I said, “Half of it?“ He said, “No.”
I said, “One-third of it?“ He said, “You may do so, though one-third is also too much.
In the Qur’an there is no evidence that a fixed fraction of 1/3 is reserved for non heirs and it also a falsehood the testator can will to anybody he pleases as priority against any of his close family members.
The writing of the will to inherit the estate of the decreased give priority to close family members on the parents, wife and children as foremost.
The brothers and sisters will only replace as an inheritor to be written in the will when those close family members mentioned above are absent.
Proofs in the Qur’an that family members have priority over non-family member or charitable causes to qualify to be written in a will.
In the case of the absolute loner who was raised in an orphanage he is entitled to make a will to inherit his estates to anybody or charitable causes as he wishes up to 100% of his estates while he is not binded as having no close relatives.
The verse below exposed those who wrote their will according to their whims and fancies and those who fixed 1/3 of his estate to non heirs.
S4:176 They ask thee for a legal decision. Say: Allah directs about those who leave no descendants or ascendants as heirs. If it is a man that dies, leaving a sister but no child, she shall have half the inheritance: If (such a deceased was) a woman, who left no child, Her brother takes her inheritance: If there are two sisters, they shall have two-thirds of the inheritance (between them): if there are brothers and sisters, (they share), the male having twice the share of the female. Thus doth Allah make clear to you (His law), lest ye err. And Allah hath knowledge of all things.
In the example above the testator is a loner but have a sister but no child, no parents or wife he has to write in his will of his sister in priority to be the inheritor of 1/2 of his estate while the other 1/2 is his choice whom he pleases as commanded in the Qur’an at S4:176 below –
Case 1 -….”If it is a man that dies, leaving a sister but no child, she shall have half the inheritance…..”
In another example in S:176 a loner with no parents, no husband or child but has only a brother. As testator she is not entitled to to make a will to any others except for her brother who is entitled to inherit the whole of her estate as directed in the Qur’an –
Case 2…..”If a woman, who left no child, Her brother takes her inheritance:”…..
The evidence above expose the falsehood those who believe to write their will on their own whims and fancies and those who fixed 1/3 portion can be willed to non heirs.
In the third example quoted below in S4:176 the testator have no parents, no husband or wife or child but have sisters and brothers, the available balance of 1/3 can be willed to non-heirs.
Case 3. …..”If there are two sisters, they shall have two-thirds of the inheritance (between them): if there are brothers and sisters, (they share), the male having twice the share of the female.”……..
The evidences above shows that in writing a will close family members are compulsory to the inheritors of the portion according to the distribution determined by Allah. The portions for non heirs is only available on the absence of the portions of the inheritors mentioned in the Qur’an.
Pondering with Saifuddin's index 