Is the niṣāb calculated based on the price of 21-karat gold, or 24-karat gold?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Zakāh is obligatory on cash and on gold designated for saving or for trade, provided the total reaches the niṣāb (minimum threshold liable for zakah), and a full ḥawl (lunar year) has elapsed over it. The niṣāb is (85) grams of 24-karat gold; for 21-karat gold, the niṣāb equals (97) grams; and for 18-karat gold, it equals (113) grams.
The relied-upon position is to calculate the zakāh based on the buying price [i.e., the price the gold merchant would pay the owner to purchase the gold from him] on the day the zakāh obligation is due.
The one paying zakāh may assess/calculate the niṣāb using any of the aforementioned gold karats [i.e., he may choose whichever karat standard he wishes for the purpose of the calculation]. And Allah, the Exalted, knows best.
Is it incumbent on a father to cover the marriage costs of his son if the latter couldn`t afford them?
The son should seek the help of his relatives in order to convince his father to do the aforesaid, and the father should make sure that his son doesn`t commit fornication through helping him to get married, and Allah will reward him for doing so.
What is the ruling of Islamic Law on performing prayer on the upper floors of al-Masjid al-Ḥarām?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Facing the actual structure of the Ka‘bah (‘ayn al-Ka‘bah) is one of the conditions for the validity of the prayer. The scholars have clarified what is meant by "the actual structure of the Ka‘bah."
Imam ash-Sharwānī (raḥimahullāh) said: "What is meant by its ‘ayn (actual structure) is its physical body, or the airspace directly aligned with it — if the person praying is not inside it. But if he is inside it, then the airspace alone does not suffice; rather, the actual physical structure must be faced, such that even if he faces a projecting part of it measuring roughly two-thirds of a dhirā‘ (cubit) or more, this would be sufficient." [Ḥāshiyat ash-Sharwānī ‘alā Tuḥfat al-Muḥtāj, Vol.1/P.484]
Sheikh al-Qulyūbī (raḥimahullāh) said: "Unlike one who prays outside it — i.e., outside the Ka‘bah — for him the airspace (directly above it) suffices, even if he is higher than it, or even if he is at the location where it (hypothetically) has been demolished." [Ḥāshiyat al-Qulyūbī ‘alā Sharḥ al-Minhāj, Vol.1/P.154]
Accordingly, the prayer is valid on the upper floors of al-Masjid al-Ḥarām, even though these floors are higher than the roof of the Ka‘bah itself. And Allah, the Exalted, knows best.
What is the ruling on performing dry ablution (tayammum) instead of the ritual bath due to severe cold?
Whoever is sick such that he cannot use water, or finds the water cold and heating it is not possible, and the person would be harmed by using cold water, it is permissible for him to perform tayammum. He must make up what he prayed with tayammum, because this is a place where there is water. And Allah the Almighty knows best.