Is it permissible to work as a freelance physician to issue a cremation permit, knowing that this work is optional and paid, and that the decision to cremate is made by the deceased's family and not by the physicians?

It is not permissible to cremate the bodies of the deceased, even if they requested it or their families desired it, because it is an abomination that contradicts the honoring of the human being and the preservation of their sanctity, alive and dead. Burial is the divine law that Allah has taught us.