What are the Sunnahs and etiquettes related to the slaughtering of an animal?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
1-Avoid terrifying the animal before it is slaughtered.
2-Do not slaughter the animal in front of others of its kind.
3-Offer water to the animal before the sacrifice.
4-Sharpen the knife thoroughly prior to slaughtering to ensure the cut is made as quickly and cleanly as possible. This is in accordance with the statement of our Master, the Prophet (peace and blessings be upon him): "Indeed, Allah, the Almighty and Majestic, has prescribed excellence (Ihsan) in all things. So when you kill, kill well; and when you slaughter, slaughter well. Let each of you sharpen his blade, and let him put his sacrificial animal at ease." (Narrated by Muslim)
Do not begin skinning the carcass until you are absolutely certain that the animal has completely passed away.
Slaughter cattle, sheep, and goats while they are lying down on their left side, facing the Qiblah (direction of prayer). Leave the right leg untied so the animal can move it, helping it rest more easily during its final moments. For camels, however, the preferred method (Nahr) is to slaughter them while they are standing up, with their left knee tied. And Allah the Almighty Knows Best.
Is it permissible to eat from an Udhiyah slaughtered on behalf of a deceased person?
Praise be to Allah, and prayers and peace be upon our Master the Messenger of Allah.
It is permissible to eat from the sacrifice (uḍḥiyyah) that is offered on behalf of a deceased person. This is the madhhab (school of thought) of the Hanbalis. In this case, the heirs take the place of the deceased as if he were alive, with the same rights to eat from it, give it in charity, and offer it as a gift.
It is stated in Maṭālib Uli al-Nuhā (Vol.2/P.472): "Offering a sacrifice on behalf of a deceased person is better than offering one on behalf of a living person, because the deceased is unable (to perform deeds) and is in need of reward. It is to be treated like a sacrifice on behalf of a living person in terms of eating, giving charity, and giving gifts." And Allah Almighty knows best.
What should the one performing the slaughter say at the time of slaughtering the 'aqīqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is Sunnah to say the following supplication at the time of slaughtering the 'aqīqah:
"Bismillāhi wallāhu Akbar, Allāhumma laka wa ilayka, hādhihi 'aqīqatu fulān."
("In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of [the child's name].")
This is based on what al-Bayhaqī narrated in Al-Sunan al-Kubrā (Vol.9/P.511), that the Prophet ﷺ said: "Slaughter it in his name and say: In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of so-and-so."
And Allah Almighty knows best.
What is the ruling on wiping the head during ablution from behind a barrier like a headscarf (hijab)?
The obligation in ablution is to wipe some of the head; it is not a condition to wipe all of it. As for one who has a turban or headscarf on their head, it is permissible for them to wipe over it after wiping a part of their head in any place. This is easily done at the front of the head. This means the woman begins by wiping the front of her head from under the headscarf, then completes the wiping to the back of the head from over the headscarf. If the woman wipes over the headscarf on her head and the moisture reaches the scalp or some hair within the boundaries of the head, it suffices for wiping the head. And Allah the Almighty knows best.