Is it valid to share in the 'aqīqah by contributing a seventh share of a camel or cow?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
Yes, it is permissible. If a group of people jointly share in the slaughter of a camel or a cow on behalf of seven individuals, this is valid — regardless of whether all of them intend the 'aqīqah, or some intend the 'aqīqah, others the uḍḥiyyah, and others simply the purchase of meat. And Allah Almighty knows best.
What should a person, who doubts the validity of his Wudu, or over performs it, do?
One who doubts the validity of his/her Wudu while performing it should redo it until he/she is certain of having attained purity. But, if doubt was after having performed Wudu, then he/she should not pay attention to that as doubt after the end of an act of worship does not count. This is of course in case doubt was within the reasonable limits since once it goes beyond that, it becomes a whispering of the Shaytaan (devil) which he/she should ignore as the Wudu is valid.
What is the ruling of Islamic Law on compensating the patient in case of medical error on the part of the treating physician?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
The foundational principle is that every mistake issued by a physician that causes harm to another due to his negligence or lack of expertise obligates him to guarantee liability and compensate the harmed party. The Sharia maxim, in this regard, states: "The direct actor is liable."
Ibn Qudamah (may Allah have mercy on him) says: "As for if he was skilled but his hand committed an error—such as exceeding the proper limit of incision, cutting in an incorrect site, cutting with an instrument that inflicts excessive pain, or cutting at an unsuitable time—he is liable, because it is destruction (Itlaf) whose liability does not differ between intent and mistake, thus resembling the destruction of property; and because it is a prohibited act, so he guarantees liability for its secondary effects." [Al-Mughni].
However, if the physician performed what was necessary in the most complete manner and took all measures of care and caution, but complications occurred that could not be avoided according to specialists, then no liability rests upon him.
Shaykh al-Islam Imam al-Nawawi (may Allah have mercy on him) says: "The cupper and the circumciser bear no liability if they have not been negligent, and likewise the veterinarian if he bleeds an animal and it perishes." [Rawdat al-Talibin].
Al-Khattabi (may Allah have mercy on him) said: "I know of no disagreement that if the practitioner transgresses and the patient perishes, he is liable. Anyone who undertakes knowledge or practice he does not know is a transgressor; so if perishing arises from his action, he is liable for the blood-money (Diyah) while capital retaliation (Qisas) is dropped from him, because he did not act independently without the patient's permission. And the physician’s offense in the view of the generality of jurists is borne by his agnates ('Aqilah*)."* [Ma'alim al-Sunan].
If negligence or transgression is established against the physician, it is necessary to compensate the patient or seek forgiveness from him. And Allah Almighty knows best.
Is it permissible for one who sacrifices on behalf of another, with the latter's permission, to eat from the sacrifice?
It is permissible for someone who sacrificed on behalf of another with their permission to eat from it with their permission, and they stand in their place (act as their representative) in distributing it.
It is stated in Nihayat al-Muhtaj ila Sharh al-Minhaj (Vol.8/P.141): "And he—meaning the one sacrificing on his own behalf, provided he has not apostatized—has the right to eat from a voluntary sacrifice and his sacrificial gift; rather, it is recommended. As for an obligatory sacrifice, it is forbidden for him to eat from it, whether it was designated as such initially or as a liability in his dhimmah. And excluded by what has preceded is if he sacrifices on behalf of another, or if he apostatized, then it is not permissible for him to eat from it, just as it is absolutely impermissible to feed a disbeliever from it."(The text I found indicates the impermissibility of eating) ???
And it is stated in Hashiyat al-Jamal ‘ala Sharh al-Manhaj (Vol.5/P.262): "If a person offers a sacrifice on behalf of a living person with their permission, does he act as their representative in distributing it—on the grounds that permission to sacrifice is permission to distribute it—or does it depend on their explicit permission? This requires consideration, but the first view is not far-fetched." And Allah the Almighty knows best.