Question: A man has a sister, and she has an inheritance with him. He wishes to rid himself of that inheritance. Whenever he asks her to come for the division, or asks her to appoint an agent, she absolutely refuses, weeps, and swears that she will not divide with her brother, and that she wants nothing of the inheritance, neither little nor much. However, the brother wants to free himself from responsibility regarding the inheritance. How is he to proceed in dividing the estate?
Answer – and Allah is the One who grants success: If the brother wants the division, then let him bring together all the partners jointly owning the estate, and let them choose two just men to enumerate and value the estate. Then let them choose for themselves a just divider (qassām). Then the brother appoints an agent on behalf of his sister, or the brother himself acts as his sister’s agent; for he has the right to do that, since his sister’s apparent renunciation of her share in his favour implies authorizing him to dispose of it as he wishes.
On this basis, the divider designates the share of each heir separately, and designates the sister’s share separately, and it is written in an independent document, with its scribe and its witnesses; then he hands this document to his sister in her own hand.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2