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.
What is the ruling on men wearing rings (those made of silver and of other metals, such as iron), and are there conditions for men wearing rings?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
It is sunnah for men to wear a silver ring on the right hand, following the practice of the Prophet (peace and blessings be upon him). It is reported in Ṣaḥīḥ al-Bukhārī, on the authority of Anas ibn Mālik (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) took a silver ring and had “Muḥammad Rasūl Allāh” engraved on it. He said: “I have taken a ring of silver and had ‘Muḥammad Rasūl Allāh’ engraved on it, so let no one engrave the like of its engraving.”
It is a condition that the silver ring not exceed the size customary in the local norm (ʿurf). If it does, that is extravagance (isrāf). A ring made of a metal other than silver, such as iron or copper, is permissible to wear without disapproval (karāhah), except gold, which is forbidden (ḥarām) for a man to wear.
It is stated in Mughnī al-Muḥtāj (Vol.1/p.586): “It is permissible, without disapproval, to wear a ring of iron or lead. It is sunnah for a man to wear a silver ring on the little finger of his right or left hand. Wearing it on the right is better, and it is permissible on the left, and on both together.”
It is also stated in Mughnī al-Muḥtāj (Vol.2/p.97): “It is lawful for him, that is, the man, and likewise the khunthā (person of indeterminate sex), indeed all the more so, to wear a ring of silver, by consensus (ijmāʿ), because the Prophet (peace and blessings be upon him) took a ring of silver, narrated by the two Shaykhs (al-Bukhārī and Muslim). Wearing it is in fact sunnah, whether on the right or the left, though the right is better according to the sound position, as stated in the chapter on clothing in al-Rawḍah… The Shāfiʿī jurists did not specify the permitted size of the ring, and they probably relied on custom (ʿurf), that is, the custom of that country and the habit of people of his standing in it. Whatever exceeds that is extravagance, as they said regarding a woman’s anklet. This is the reliable position (al-muʿtamad).” And Allah Almighty knows best.
What is the ruling on eating and drinking at night after making the intention? Is it necessary to renew the intention?
Eating and drinking at night, even after making the intention (for the next day), does not affect the fast, and it is not necessary to renew the intention after eating and drinking.
What is the ruling on praying in congregation at the mosque?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Congregational prayer (Salat al-Jama‘ah) is a communal obligation (Fard Kifayah) for resident men regarding the performance of the prescribed (obligatory) prayers. For men, praying in congregation at the mosque is better than praying elsewhere, such as at home. On the authority of Abdullah bin Umar, the Messenger of Allah ﷺ said: 'Prayer in congregation is twenty-seven degrees more excellent than the prayer of a person alone' (Reported by Bukhari & Muslim). Furthermore, on the authority of Abu Hurayrah, the Messenger of Allah ﷺ said: 'Shall I not tell you that by which Allah erases sins and raises ranks?' They said, 'Of course, O Messenger of Allah.' He said: 'Performing wudu thoroughly despite difficulties, taking many steps toward the mosques, and waiting for the next prayer after the prayer; that is your Ribat (steadfastness)' (Narrated by Muslim).
As for a woman, her praying in congregation at home is better for her than in the mosque, according to the saying of our Master the Prophet ﷺ: 'Do not prevent your women from attending the mosques, but their homes are better for them' (Narrated by Abu Dawood). Young boys should be encouraged to attend the mosques and congregational prayers so they may become accustomed to them. And Allah the Exalted knows best.