But he who fears from a testator some unjust act or wrongdoing, and thereupon he makes peace between the parties concerned, there shall be no sin on him. Certainly, Allah is Oft-Forgiving, Most Merciful.
فَمَنْ خَافَ مِن مُّوصٍ جَنَفًا أَوْ إِثْمًا
(But he who fears from a testator some unjust act or wrongdoing),
Ibn Abbas, Abu Al-Aliyah, Mujahid, Ad-Dahhak, Ar-Rabi bin Anas and As-Suddi said,
"Error."
These errors include such cases;
as when the inheritor indirectly acquires more than his fair share, such as by being allocated that a certain item mentioned in the legacy be sold to him.
Or, the testator might include his daughter's son in the legacy to increase his daughter's share in the inheritance, and so forth.
Such errors might occur out of the kindness of the heart without thinking about the consequences of these actions, or by sinful intention.
In such cases, the executive of the will and testament is allowed to correct the errors and to replace the unjust items in the will with a better solution, so that both the Islamic law and what the dead person had wished for are respected and observed. This act would not constitute an alteration in the will and this is why Allah mentioned it specifically, so that it is excluded from the prohibition (that prohibits altering the will and testament) mentioned in the previous Ayah.
And Allah knows best.
The Virtue of Fairness in the Will
Abdur-Razzaq reported that Abu Hurayrah said that Allah's Messenger said;
إِنَّ الرَّجُلَ لَيَعْمَلُ بِعَمَلِ أَهْلِ الْخَيْرِ سَبْعِينَ سَنَةً فَإِذَا أَوْصَى حَافَ فِي وَصِيَّتِهِ فَيُخْتَمُ لَه بِشَرِّ عَمَلِهِ فَيَدْخُلُ النَّارَ
وَإِنَّ الرَّجُلَ لَيَعْمَلُ بِعَمَلِ أَهْلِ الشَّرِّ سَبْعِينَ سَنَةً فَيَعْدِلُ فِي وَصِيَّتِهِ فَيُخْتَمُ لَهُ بِخَيْرِ عَمَلِهِ فَيَدْخُلُ الْجَنَّــة
A man might perform the works of righteous people for seventy years, but when he dictates his will, he commits injustice and thus his works end with the worst of his deeds and he enters the Fire.
A man might perform the works of evil people for seventy years, but then dictates a just will and thus ends with the best of his deeds and then enters Paradise.
Abu Hurayrah then said, "Read if you wish;
تِلْكَ حُدُودُ اللَّهِ فَلَ تَعْتَدُوهَا
These are the limits ordained by Allah, so do not transgress them." (2;229