Ibn Ishaq محمد بن إسحاق بن يسار‎ · Shares of Inheritance (Kitab Al-Fara'id)

The Messenger of Allah (ﷺ) forbade selling or giving away the right to inheritance by a manumitted slave.

"To those also, to whom your right hand was pledged, give your portion." When the Emigrants came to Medina. they inherited from the Helpers without any blood-relationship with them for the brotherhood which the Messenger of Allah (ﷺ) established between them. When the following verse was revealed: "To (benefit) everyone we have appointed shares and heirs to property left by parent and relatives." it abrogated the verse: "To those also, to whom your right hand was pledged, give their due…