What should one who doubts the validity of his ablution and performs it frequently do?
Whoever doubts the validity of his ablution after finishing it, his ablution is valid. This is because the default is the validity of the ablution, and because doubt after finishing an act of worship doesn`t affect its validity. And Allah the Almighty knows best.
What is the ruling on someone who possesses cash reaching the niṣāb (minimum threshold liable for zakah), and then uses part of it to purchase gold before the ḥawl (lunar year) is complete — must he pay zakāh on all of it [combined], or only on the remaining cash, excluding the gold?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Gold acquired for hoarding and saving is subject to zakāh once it reaches the niṣāb (minimum threshold liable for Zakah) — when combined with any cash held — and once a full ḥawl (lunar year) has elapsed over it. The starting point for calculating this ḥawl is the ḥawl of the paper currency [used to purchase it], which had already reached the niṣāb and was then used to purchase the gold.
It is stated in Mughnī al-Muḥtāj (Vol.2/p.78): "As for someone who sells silver in exchange for gold, or vice versa, zakāh remains obligatory upon it, since he builds [the calculation of] its ḥawl upon [the ḥawl established at the time of] the original transaction [i.e., when the wealth was first acquired]."
This has already been explained in detail in Fatwa No.
2670 — please refer to it.
And Allah, the Exalted, knows best.
What is the ruling on performing the Witr prayer as a single rak`ah?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
It is permissible to perform the Witr prayer as a single unit (rak‘ah). It was narrated from Ibn ‘Umar that a man asked the Messenger of Allah ﷺ about the night prayer, and the Messenger of Allah ﷺ replied: 'The night prayer is offered two by two (mathna mathna). If one of you fears the approach of dawn, let him pray a single rak‘ah to make what he has prayed odd-numbered (Witr) for him.' (Related by al-Bukhari & Muslim)). However, limiting the prayer to only one rak‘ah is considered 'contrary to the preferred way' (Khilaf al-Awla).
It is stated in Al-Minhaj al-Qawim Sharh al-Muqaddimah al-Hadramiyyah (p. 137): 'The minimum of Witr is one rak‘ah, but limiting it to that is contrary to what is best.'
The most complete form of Witr is eleven units, while the minimum level of 'perfection' is three units. It is stated in ‘Umdat al-Salik (p. 60): 'The minimum of Witr is one rak‘ah, and its maximum is eleven, performing the taslim (salutation) after every two units. The lowest level of perfection is three units with two separate taslims (meaning 2+1).' And Allah the Exalted knows best.
Is it permissible to purchase the Udhiyah on installments?
It is permissible to purchase the sacrificial animal (uḍḥiyyah) on installments or by borrowing its price. However, it is not recommended for the poor to do so, because they are not required to offer a sacrifice, and Allah does not burden a soul beyond its capacity. If doing so would lead to negligence in providing for one's dependents (nafaqah wājibah), then giving precedence to obligatory maintenance over borrowing to buy the sacrifice is appropriate. This is based on the saying of the Prophet (peace and blessings be upon him): "It is sufficient sin for a person to withhold food from those whom he is responsible to support."
Furthermore, the sacrifice is valid from one who has a debt, but it is preferable (awlā) to repay the debt first, especially if the debt is due immediately (ḥāll). And Allah Almighty knows best.