[A man was killed, and his son took from the estate the expenses of taking revenge]

The answer: It is not permissible for him to take the expenses from the principal of the estate unless the rest of the heirs give him permission for that, or appoint him as their agent in demanding retribution. If they do not give him permission for that and do not appoint him as their agent, then he may not take from the principal of the estate. If he has already taken (from it) for that purpose, then he must inform them; if they are pleased (with that), then so be it, otherwise he has no right except with their consent.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2