If a person enters a mosque and finds the congregation in the final tashahhud, which is more virtuous — joining them or waiting for a second congregation to catch the opening takbīr (takbīrat al-iḥrām)?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
If a worshipper finds a congregation that is about to finish its prayer, and he hopes to catch the entire prayer from the beginning with another congregation, it is more virtuous for him to pray with this first congregation and then repeat the prayer with the second one — provided he does not intend to confine himself to a single prayer. If, however, he intends to perform only one prayer, then it is more virtuous for him to wait for the second congregation rather than joining the first, so that he may attain the reward of congregational prayer for every single rakʿah.
Al-Khaṭīb al-Sharbīnī, may Allah have mercy upon him, states: "If members of a congregation enter the mosque while the imam is in the final tashahhud, al-Qāḍī Ḥusayn held that it is recommended for them to join him in prayer, and that they should not delay in order to form a second congregation. Al-Mutawallī, however, affirmed the opposite view, and al-Qāḍī's own statement elsewhere supports this latter position, which is the relied-upon view. In fact, it is more virtuous for a person who has missed part of the prayer with one congregation, and who hopes to catch another congregation with whom he can attain the entire prayer within its proper time, to delay so that he may catch it in full with them. This applies when he intends to confine himself to a single prayer; otherwise, it is more virtuous for him to pray with the first group and then repeat the prayer with the others." [Mughnī al-Muḥtāj,Vol. 3/P.186] And Allah the Almighty knows best.
What is the due amount of food in expiation for perjury?
It is feeding ten indigent persons: 600 grams (for each) of the average food of your families such as rice, and it is permissible, according to Imam Ahmad Bin Hanbal, to give that amount in money if it was more useful to them.
What is the ruling on congregational prayer performed outside the mosque, and is it a condition that it be performed in a mosque in order to attain the full reward?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
It is not a condition for attaining the reward of congregational prayer that it be performed in a mosque; however, a Muslim should still be keen to perform his prayers in the mosque, so as not to miss out on immense reward. This is due to the virtue of the mosque and of spending time there (i‘tikāf), the typically larger number of worshippers present, and the additional reward gained through walking to and from the mosque. On the authority of Abū Hurayrah (raḍiyallāhu ‘anh), the Messenger of Allah ﷺ said: "Whoever purifies himself in his house, then walks to one of the houses of Allah to fulfill one of the obligations Allah has prescribed, one of his steps will erase a sin, and the other will raise him a degree [in status]." (Related by Muslim)
Whoever misses congregational prayer at the mosque should still strive to pray in congregation at his workplace, or together with the members of his household. And Allah, the Exalted, knows best.
Who is responsible for performing the aqiqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
The one upon whom the 'aqīqah is incumbent is whoever is obligated to financially maintain the newborn — whether the father, paternal grandfather, or mother. It is to be performed from their own wealth, not from the wealth of the newborn child.
As for one upon whom the financial maintenance of the newborn is not obligatory, they may not perform the 'aqīqah except with the permission of the one upon whom it is obligatory — namely, the father. And Allah Almighty knows best.