Sahih al-Bukhari 4580
Narrated Ibn `Abbas:
Regarding the Verse: "To everyone, We have appointed heirs." (4.33) 'Mawali' means heirs. And 
regarding:-- "And those to whom your right hands have pledged." 
When the Emigrants came to Medina, an Emigrant used to be the heir of an Ansari with the exclusion 
of the latter's relatives, and that was because of the bond of brotherhood which the Prophet (ﷺ) had 
established between them (i.e. the Emigrants and the Ansar). So when the Verses:-- "To everyone We 
have appointed heirs." was revealed, (the inheritance through bond of brotherhood) was cancelled. Ibn 
`Abbas then said: "And those to whom your right hands have pledged." is concerned with the 
covenant of helping and advising each other. So allies are no longer to be the heir of each other, but 
they can bequeath each other some of their property by means of a will.
حَدَّثَنِي الصَّلْتُ بْنُ مُحَمَّدٍ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ إِدْرِيسَ، عَنْ طَلْحَةَ بْنِ مُصَرِّفٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاس ٍ ـ رضى الله عنهما ـ ‏{‏وَلِكُلٍّ جَعَلْنَا مَوَالِيَ‏}‏ قَالَ وَرَثَةً‏.‏ ‏{‏وَالَّذِينَ عَاقَدَتْ أَيْمَانُكُمْ‏}‏ كَانَ الْمُهَاجِرُونَ لَمَّا قَدِمُوا الْمَدِينَةَ يَرِثُ الْمُهَاجِرُ الأَنْصَارِيَّ دُونَ ذَوِي رَحِمِهِ لِلأُخُوَّةِ الَّتِي آخَى النَّبِيُّ صلى الله عليه وسلم بَيْنَهُمْ فَلَمَّا نَزَلَتْ ‏{‏وَلِكُلٍّ جَعَلْنَا مَوَالِيَ‏}‏ نُسِخَتْ، ثُمَّ قَالَ ‏{‏وَالَّذِينَ عَاقَدَتْ أَيْمَانُكُمْ ‏}‏ مِنَ النَّصْرِ، وَالرِّفَادَةِ وَالنَّصِيحَةِ، وَقَدْ ذَهَبَ الْمِيرَاثُ وَيُوصِي لَهُ‏.‏ سَمِعَ أَبُو أُسَامَةَ إِدْرِيسَ، وَسَمِعَ إِدْرِيسُ طَلْحَةَ‏.‏