Sahih Bukhari | Volume 8 | Hadith Number 739

Narrated by Ibn 'Abbas
Regarding the Holy Verse: "And to everyone, We have appointed heirs..." (4:33) And: "To those also to Whom your right hands have pledged." (4:33)

When the emigrants came to Medina, the Ansar used to be the heir of the emigrants (and vice versa) instead of their own kindred by blood (Dhawl-l-arham), and that was because of the bond of brotherhood which the Prophet had established between them, i.e. the Ansar and the emigrants. But when the Divine Verse:

And to everyone We have appointed heirs," (4:33) was revealed, it cancelled the other order, i.e. "To those also, to whom Your right hands have pledged."