وَالَّذِينَ آمَنُوا مِن بَعْدُ وَهَاجَرُوا وَجَاهَدُوا مَعَكُمْ فَأُولَٰئِكَ مِنكُمْ ۚ وَأُولُو الْأَرْحَامِ بَعْضُهُمْ أَوْلَىٰ بِبَعْضٍ فِي كِتَابِ اللَّهِ ۗ إِنَّ اللَّهَ بِكُلِّ شَيْءٍ عَلِيمٌ (75)
(8:75) And those who believed afterwards and migrated and strove along with you: they belong to you. But those related by blood are nearer to one another according to the Book of Allah. *53 Allah has knowledge of everything.
*53). The purpose of the verse is to make it clear that the basis of inheritance is blood relationship and marriage rather than the mere bond of Islamic brotherhood. What occasioned this statement was the misunderstanding which had arisen after migration to Madina, when the Prophet (peace be on him) established fraternal relations between the Ansar and the Muhajirun and made pairs of them declaring that they were 'brothers' of each other. (See Ibn Hisham, vol. 1, pp. 504-6 - Ed.)