What do those who think that prayers in qiyaam al-layl should be offered two (rak‘ahs) by two say about the hadeeth of Mu‘aadh ibn Jabal (may Allah be pleased with him)?
Question

Is it permissible to offer the night prayers with four rak‘ahs and one salaam? I heard that one of the Sahaabah used to pray ‘Isha’ with the Prophet (blessings and peace of Allah be upon him), then he would go back to his people and lead them in praying another ‘Isha’ which was naafil for him. If that is not permissible, then how are we to interpret this hadeeth which tells us about this Sahaabi?
Praise be to Allah.Firstly: 
The fuqaha’ differed concerning the description of qiyaam al-layl – in terms of how many rak‘ahs it is. There are two views: 
The first view: 
The first view is that it is mustahabb in qiyaam al-layl to say the tasleem after four rak‘ahs, not after two, but if a person prays two rak‘ahs, that is valid and there is no blame on him. This is the view of Imam Abu Haneefah (may Allah have mercy on him). 
Imam as-Sarkhasi (may Allah have mercy on him) said: 
Voluntary prayers at night may be offered two (rak‘ahs) by two, or four by four, or six by six, or eight by eight, however one wishes, because of the report that the Prophet (blessings and peace of Allah be upon him) used to pray five rak‘ahs at night, or seven rak‘ahs, nine rak‘ahs, eleven rak‘ahs or thirteen rak‘ahs. 
Four is preferable. This is the view of Abu Haneefah (may Allah have mercy on him). 
We also have the report narrated from ‘Aa’ishah (may Allah be pleased with her), according to which she was asked about the qiyaam of the Messenger of Allah (blessings and peace of Allah be upon him) during the nights of Ramadan, and she said: His qiyaam during Ramadan and at other times was the same. After ‘Isha’ he used to pray four rak‘ahs, and do not ask how beautiful and long they were. Then (he would pray) four rak‘ahs, and do not ask how beautiful and long they were. Then he would pray Witr with three (rak‘ahs). 
Because praying four (rak‘ahs) with one tasleem implies continuity in worship, it is preferable. 
The voluntary prayers are akin to the obligatory prayers, and the obligatory prayer of the night prayer is ‘Isha’, which has four (rak‘ahs) with one tasleem; therefore the same applies to the naafil prayer. 
End quote from al-Mabsoot (1/158) 
The second view: 
The second view is that the night prayer should be done two (rak‘ahs) by two, so that the tasleem is said after every two rak‘ahs. This is the view of the Hanbalis. And if a person does more than two rak‘ahs, his prayer becomes invalid. 
Ibn Qudaamah (may Allah have mercy on him) said: 
The voluntary prayers are to be done two (rak‘ahs) by two, i.e., one should say the tasleem after every two rak‘ahs. Voluntary prayers are of two types: voluntary prayers at night and voluntary prayers by day. With regard to the voluntary prayers at night, it is not permissible to do them except two (rak‘ahs) by two. This is the view of most of the scholars, and it is also the view of Abu Yoosuf and Muhammad. Abu Haneefah said: If you wish you may do two rak‘ahs, or if you wish you may do four, or if you wish you may do six, or if you wish you may do eight. 
But we have (in support of our view) the words of the Prophet (blessings and peace of Allah be upon him): “The night prayers are two (rak‘ahs) by two.” Agreed upon. And it was narrated from ‘Aa’ishah that the Messenger of Allah (blessings and peace of Allah be upon him) said: “The key to prayer is purification, and after every two (rak‘ahs) there should be a tasleem.” Narrated by al-Athram.
End quote from al-Mughni (2/91). 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 
If the prayers of night and day are two (rak‘ahs) by two, then what is the ruling if a person gets up for a third (rak‘ah)? 
The answer is that his prayer becomes invalid if he does that deliberately, because if he deliberately does more than two, he has gone against the command of the Messenger of Allah (blessings and peace of Allah be upon him), which indicates that the night prayers are two (rak‘ahs) by two, and if he goes against the command of the Messenger of Allah (blessings and peace of Allah be upon him), the Prophet (blessings and peace of Allah be upon him) said: “Whoever does an action that is not in accordance with this matter of ours, it will be rejected.” Hence Imam Ahmad said: If he gets up for a third (rak‘ah) in the night prayer, it is the same as if he gets up for a third (rak‘ah) in Fajr prayer. It is well-known that if he gets up for a third (rak‘ah) in Fajr prayer deliberately, his prayer becomes invalid according to scholarly consensus. The same applies if he gets up for a third (rak‘ah) in a voluntary night prayer: his prayer becomes invalid if he did that deliberately. 
End quote from ash-Sharh al-Mumti‘ ‘ala Zaad al-Mustaqni‘ (4/77) 
The third view: 
The third view is that it is mustahabb for the night prayers to be done two (rak‘ahs) by two, but it is not obligatory. If a person says the tasleem after four (rak‘ahs), his prayer is valid and there is no blame on him, but he has done something contrary to what is preferred. This is the view of the Maalikis and Shaafa‘is, although there is a slight difference between them. 
An-Nafraawi al-Maaliki (may Allah have mercy on him) said: 
His naafil prayer should be two rak‘ahs by two, and it is makrooh for him to pray four rak‘ahs without a tasleem between each two. 
End quote from al-Fawaakih ad-Dawaani (1/201). 
Imam an-Nawawi (may Allah have mercy on him) said: 
It is preferable to say tasleem after every two rak‘ahs, and the naafil prayers of the night and day are the same: it is mustahabb to say the tasleem after every two rak‘ahs. But if he does a number of rak‘ahs with one tasleem, or he prays one rak‘ah of voluntary prayer, that is permissible in our view. 
End quote from Sharh Muslim (6/30) 
Imam ar-Ramli ash-Shaafa‘i (may Allah have mercy on him) said: 
It is best for the one who offers naafil prayers during the night or during the day to say the tasleem after every two rak‘ahs, by intending to pray two rak‘ahs from the outset, or by limiting it to two rak‘ahs when he does not specify anything (in his intention), because of the report, “The prayers of the night and day are two (rak‘ahs) by two.” What is meant by that is that one should say the tasleem after every two rak‘ahs. Obviously, it does not mean that Zuhr, for example, should be two (rak‘ahs) by two. But to do naafil prayers with an odd number of rak‘ahs it is not mustahabb. 
End quote from Nihaayat al-Muhtaaj (2/130). Ash-Shabramalsi commented in his footnote on the words “it is not mustahabb” by saying: and it is not makrooh either, even if it is only one (rak‘ah). End quote. 
See also the answer to question no. 45268 
Secondly: 
With regard to the Sahaabi who used to pray ‘Isha’ with the Prophet (blessings and peace of Allah be upon him) then after that go to his people and lead them in praying ‘Isha’, he was Mu‘aadh ibn Jabal (may Allah be pleased with him). Al-Bukhaari (6106) and Muslim (465) narrated from Jaabir ibn ‘Abdullah (may Allah be pleased with him) that Mu‘aadh ibn Jabal used to pray ‘Isha’ with the Messenger of Allah (blessings and peace of Allah be upon him), then he would go back to his people and lead them in that prayer. 
It does not seem that the hadeeth of Mu‘aadh ibn Jabal comes under the heading of voluntary prayers in general, whether by night or by day. Rather it comes under another heading, which is that of voluntary prayers by repeating an obligatory prayer in order to attain some Islamically-prescribed virtue, either by joining a congregation when one has prayed on one’s own, or by giving charity to one who is praying alone, so that he will then be praying in congregation (and attain an increased reward), as in the hadeeth narrated by Abu Dawood (574) from Abu Sa‘eed al-Khudri, according to which the Messenger of Allah (blessings and peace of Allah be upon him) saw a man praying by himself, and he said: “Will any man give charity to this one and pray with him?” classed as saheeh by Shaykh al-Albaani in Saheeh Sunan Abi Dawood. 
Ibn ‘Abd al-Barr (may Allah have mercy on him) said: 
These hadeeths indicate that the first was obligatory and the second was voluntary (for him). It also indicates that repeating a prayer with the imam is something general in application that anyone may do, and is not limited to a specific situation.
End quote from at-Tamheed (4/257) 
Majd ad-Deen Ibn Taymiyah included this and similar hadeeths in a chapter in al-Muntaqa entitled “Chapter on the concession allowing one to repeat prayers offered in congregation and the two rak‘ahs following tawaaf at any time.” 
Ash-Shawkaani (may Allah have mercy on him) said: 
What appears to be the case is that it makes no difference whether the first prayer was offered in congregation or individually, because the hadeeth does not indicate that there is a difference, therefore it is general in application.  However Ibn ‘Abd al-Barr said: The majority of fuqaha’ said: The only one who may repeat a prayer with the imam in congregation is the one who already offered the prayer on his own. With regard to the one who has already prayed in congregation, even if it was a small congregation, he cannot repeat his prayer with another congregation, whether it is small or large. That is because if he can repeat it with another congregation, he could then repeat it a third and fourth time, and so on without end, which does not make sense.
End quote from Nayl al-Awtaar (3/122) 
See also: al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah (27/173-175) 
It may be because the hadeeth of Mu‘aadh does not come under this heading (of naafil prayer) – and Allah knows best – that  we have not come across any scholar who quoted it as evidence to support his view that it is permissible to do more than two rak‘ahs in a naafil prayer. But those who disallow offering a naafil prayer with more than two rak‘ahs did not try to reconcile their views with this hadeeth for the same reason, that this hadeeth does not come under the heading of naafil prayer. 
And Allah knows best.