What is the ruling on doing a second congregational prayer in the mosque, according to the four madhhabs?
Question

What is the opinion on holding a second congregation in all the madhabs?
Praise be to Allah.Holding a second congregational prayer in the mosque may happen in various ways; in some cases the ruling is agreed upon, and in others there is a difference of opinion on the ruling.
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When a number of congregational prayers are held because the people are divided into different groups, sects and madhhabs, so the mosque management organises more than one congregational prayer on a permanent basis, with each group having its own imam and its own time for prayer.
This is not allowed, according to scholarly consensus.
It says in Mawahib al-Jalil by al-Hattab (may Allah have mercy on him):
As for establishing one prayer with two regular imams, where they both attend, and the one whose turn it is to pray first goes ahead and leads the prayer, whilst the other group sits and waits with their imam until the first group has finished, then they give the iqaamah for their prayer. No one has suggested that this is allowed, and it is not possible that there could be a report from any of the jurists to suggest that he did it or approved of it.
It is even worse if two imams are leading prayers at the same time, each of them saying “Hayya ‘ala as-salah (come to prayer)” and saying takbir, when those praying behind them are mixed, each of them hearing the recitation of the other? These people will cause more friction, that was not known to the early generations or those who came after them. Moreover, it is going against the words of the Messenger of Allah (blessings and peace of Allah be upon him): “Do not disturb one another with your recitation of Quran…”"(Mawahib al-Jalil  2/380).
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When there is a second congregational prayer in a mosque in which there is no regular imam, as happens in some mosques that are on travel routes. In this case, it is permissible for there to be a number of congregational prayers, according to scholarly consensus.
An-Nawawi (may Allah have mercy on him) said: With regard to the views of the scholars regarding congregational prayer in a mosque where a congregational prayer has already been offered:
If there is no regular imam, then it is not disliked (makruh) for there to be a second, third or more congregational prayer, according to scholarly consensus."(Al-Majmu‘  4/222).
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Holding a second congregational prayer for some reason, in a mosque where there is a regular imam.
The majority of Hanafi, Maliki and Shafa‘i scholars are of the view that it is disliked (makruh) to hold a second congregational prayer in this case.
An-Nawawi (may Allah have mercy on him) said: If there is a regular imam, and the mosque is not frequented, then in our view it is disliked (makruh) to hold a second congregational prayer without the permission of the imam. This is the view of ‘Uthman al-Batti, al-Awza‘i, Malik, al-Layth, ath-Thawri and Abu Hanifah.
Ahmad, Ishaq, Dawud and Ibn al-Mundhir said that it is not disliked (makruh)."(Al-Majmu‘  4/222).
Imam Abu Bakr ibn al-Mundhir (may Allah have mercy on him) said:
Chapter: The concession allowing prayer in congregation in a mosque in which the imam has already led the people in prayer.
Abu Bakr said:
We have narrated that a man entered the mosque when the Prophet (blessings and peace of Allah be upon him) had already prayed, and he said: “Will anyone be charitable towards this man and pray with him?”
There was a difference of scholarly opinion regarding that.
It is proven from Anas that he led a congregational prayer after the imam had already prayed. It was also narrated from Ibn Mas‘ud that he did the same thing. This was the view of ‘Ata’, an-Nakha‘i, al-Hasan al-Basri, Qatadah, Ahmad and Ishaq. Ahmad quoted as evidence the words of the Prophet (blessings and peace of Allah be upon him): “Prayer in congregation is twenty-seven times better than prayer offered individually.”
Some said: A congregational prayer should not be offered in the mosque twice. This is the view of Salim ibn ‘Abdillah, and also of Abu Qilabah, Ibn ‘Awn, Ayyub, ‘Uthman al-Batti, Malik, al-Layth ibn Sa‘d, Sufyan ath-Thawri, al-Awza‘i, ash-Shafa‘i, and ashab ar-ra’y.
Abu Bakr ibn al-Mundhir said: I favour the first view."(Al-Ishraf ‘ala Madhahib al-‘Ulama’  2/146-147).
This view which was favoured by Ibn al-Mundhir is the correct view, because of the evidence from the Sunnah to that effect.
Ibn al-Mundhir (may Allah have mercy on him) said elsewhere:
It is proven that the Prophet of Allah (blessings and peace of Allah be upon him) said: “Prayer in congregation is twenty-seven times better than prayer offered individually.” And it is proven that he said: “For a man to pray with another man is more appropriate than his praying on his own, and for a man to pray with three others is more appropriate; the more people there are, the more beloved it is to Allah.”
And the hadith of Abu Sa‘id [according to which a man came when the Prophet (blessings and peace of Allah be upon him) had already prayed, so he said: “Will anyone be charitable towards this man and pray with him?”] is proven.
So if some people miss the prayer with the imam, they may pray together in congregation, following the hadith of Abu Sa‘id, and seeking the virtue of praying in congregation. We do not know of any evidence for those who dislike and disallow that."(Al-Awsat  4/248).
See also the answer to question no. 87847, in which there is a fatwa from Shaykh Ibn ‘Uthaymin regarding this matter.
But to give a complete picture of this matter, we should mention the views of all the madhhabs.
Badr ad-Deen al-‘Ayni al-Hanafi (may Allah have mercy on him) said:
In our view, it is disliked (makruh) for the prayer in congregation to be repeated in the same mosque."(Al-Binayah  2/580).
Yahya ibn Yahya al-Laythi said:
Malik was asked about a mu’adhdhin who gives the call to prayer, then he waits to see whether anyone else will come, then no one comes, so he gives the iqamah (call immediately preceding the prayer) and prays by himself, then some people come after he has finished. Should he repeat the prayer with them? He said: He should not repeat the prayer. Whoever comes after he has finished praying, let him pray by himself."(Muwatta’ Malik, narrated by Yahya  1/72).
Ash-Shafa‘i (may Allah have mercy on him) said:
If the mosque has a regular imam, and one or more men missed the prayer in the mosque, they should pray individually. I do not like them to pray in congregation, but if they do that, it is valid. However, I dislike them to do that, because that is not what the earlier generations did before us, and in fact some of them criticised that action."(Al-Umm 2/292).
Please see also the answers to questions no. 87847 , 127293 and 146916 .
And Allah knows best.