Praying Maghrib behind one who is praying ‘Isha’

Rather you should join the imam in the prayer, with the
intention of praying Maghrib, then you should sit in the third rak’ah and
recite the Tashahhud and say the salaam, then join the imam in what is left
of ‘Isha’ prayer. Or wait during the Tashahhud until the imam finishes the
prayer and say the tasleem with him, then pray ‘Isha’. 

This is the view of Imam al-Shaafa’i (may Allaah have mercy
on him), and is one of the two views narrated from Imam Ahmad. Al-Mardaawi
stated in al-Insaaf (4/413) that this view was favoured by a number
of the companions of Imam Ahmad, including Shaykh al-Islam Ibn Taymiyah and
his grandfather al-Majd ibn Taymiyah. 

Al-Nawawi (may Allaah have mercy on him) said in
al-Majmoo’, 4/143: 

If he intends to pray
Fajr behind one who is praying Zuhr and the congregational prayer is
completed, if he wishes he may wait during the Tashahhud until the imam
finishes, and say the tasleem with him, which is better, or if he wishes he
may decide to leave him and say the tasleem. This leaving does not
invalidate his prayer, and there is no scholarly dispute on this point,
because he is excused from following the imam. End quote. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was
asked: 

Some worshippers were delayed in praying Maghrib, and they
found that the imam had started to pray ‘Isha’. Should they pray Maghrib in
a congregation on their own, or join the imam? And how should they pray? 

He replied: 

The correct view is that if a person comes (to the mosque)
and the imam is praying ‘Isha’, whether he is with a group or not, he should
join the imam, with the intention of praying Maghrib. It does not matter if
the imam’s intention is different from that of one who is praying behind
him, because the Prophet (peace and blessings of Allaah be upon him)
said: “Actions are but by intentions, and each person will have but that
which he intended.” If they join him in the second rak’ah, they can say the
tasleem with him, because they will have prayed three rak’ahs, and it does
not matter if they sit for the Tashahhud during their first rak’ah. If they
join him in the first rak’ah, then when he stands up for the fourth rak’ah,
they can sit and recite the Tashahhud and say the tasleem, then join him in
what remains of ‘Isha prayer. 

The second opinion concerning this matter is that they should
join him with the intention of praying ‘Isha’, then pray Maghrib after that,
and the obligation to offer the prayers in order is waived because of the
duty to join the congregation. 

The third view is that they should pray Maghrib on their own,
then join him in whatever is left of ‘Isha’ prayer. The last two views
involve something about which there is some reservation. The first view
involves neglecting the order of prayers by putting ‘Isha’ before Maghrib.
The second view involves having two congregations in one mosque at the same
time, which is dividing the ummah. 

But the first view which we mentioned is the correct one.
Someone may say that there is something wrong, which is saying the tasleem
before the imam. In fact there is nothing wrong with this. It is narrated in
some places in the Sunnah that a member of the congregation may do something
separately from the imam, such as in the fear prayer, where the imam leads
them in one rak’ah, then they complete the prayer by themselves and leave. 

Another example is the story of the man who joined Mu’aadh
ibn Jabal (may Allaah be pleased with him) in prayer, but when he started to
recite Soorat al-Baqarah or another similar soorah, he left him and did not
complete the prayer with him.  

And the scholars said
that if a man is praying in congregation then he feels that is about to pass
wind or that he needs to break his wudoo’ by urinating or defecating, then
there is no sin on him if he decides to pray alone and completes his prayer
and leaves. This indicates that praying alone in the case of need is not
regarded as wrong. End quote. 

Liqaa’aat al-Baab il-Maftooh,
3/425 

Shaykh Ibn Baaz was asked: I entered the mosque and the
‘Isha’ prayer had started. Before I joined the prayer, I remember that I had
not prayed Maghrib. Should I pray Maghrib and then catch up with ‘Isha’ with
the congregation, or should I pray with the congregation and then pray
Maghrib afterwards? 

He replied: if you enter the mosque and ‘Isha’ prayer has
started, then you remember that you did not pray Maghrib, then you should
join the congregation with the intention of praying Maghrib. When the imam
stands up for the fourth rak’ah, you should sit in the third rak’ah and
recite the final tashahhud – i.e., al-tahhiyaatu and the blessings
upon the Prophet (peace and blessings of Allaah be upon him) – and make
du’aa’ after that, then wait for the imam to say the tasleem and say the
tasleem with him. It does not matter if the imam and the member of the
congregation have different intentions, according to the sound scholarly
opinion. If you pray Maghrib on your own and then join the congregation in
what is left of ‘Isha’ prayer, there is nothing wrong with that. End quote. 

Majmoo’ Fataawa Ibn Baaz,
12/189 

The Standing Committee
was asked: what should a man do if he forgets Fajr prayer, for example, and
does not remember until the iqaamah is given for Zuhr, or he forgets Zuhr
and does not remember until the time for ‘Asr begins. Should he join the
imam with the intention of offering the obligatory prayer that he missed or
with the intention of offering the prayer that is currently due, and make up
the missed prayer after that? 

He replied: He should offer the prayer that he forgot behind
the imam, and it does not matter if his intention is different from that of
the imam, according to the sound scholarly opinion. End quote. 

Fataawa al-Lajnah al-Daa’imah,
7/407.