Assalaamu alaykum. I joined the prayer as the imam was saying Tasleem (closing the prayer) at the end of the Maghrib prayer. Because of rain, they combined the Maghrib and the `Ishaa' together. Should I perform the Maghrib before joining the congregation for the `Ishaa' prayer in such case?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If you find a congregation praying the ‘Ishaa' and you have not prayed the Maghrib yet, you have three choices:

First, you pray the Maghrib individually and then join the congregation in what remains of the `Ishaa'.

Second, you join the congregation with the intention to pray ‘Ishaa' and then you pray the Maghrib afterwards.

Third, you join the congregation with the intention of praying the Maghrib, and when the imaam finishes the third Rak‘ah (unit of prayer), you sit down and say Tashahhud and Tasleem, or you can remain sitting and wait for the imaam to say Tasleem and follow him in that and then pray the ‘Ishaa' individually afterwards.

An-Nawawi wrote:

“If the imaam is performing more Rak‘ahs than the follower, as is the case when the follower is praying Fajr with a congregation praying the Maghrib or a four-Rak‘ah prayer, then he has two options, the most correct of which is that it is permissbile, the same like its opposite (i.e. praying the Maghrib or a four-Rak'ah prayer with a congregation praying Fajr) as reported by Fiqh scholars of Khuraasaan and supported by the scholars of Iraq. According to our school of Fiqh, it is allowable for the follower praying the Fajr or Maghrib to join a four-Rak‘ah congregational prayer; so when the follower finishes his prayer and the imaam stands up to carry on with the remaining Rak`ah(s), the follower has two options. He may conclude his prayer and say Tasleem individually, or he can wait for the imaam to finish and follow him in saying Tasleem. It is better to wait for the imaam and say Tasleem after him.” [Al-Majmoo’]

Ibn ‘Uthaymeen said, “The second view in this regard is that they join the congregation with the intention of praying the ‘Ishaa' and then pray Maghrib individually afterwards. The obligation of observing the correct order of prayers is waived in this case because of the duty to join the congregation. The third view in this regard is that they pray the Maghrib individually first and then join the congregation and pray whatever is left of the ‘Ishaa' with them.” [Liqaa' Al-Baab Al-Maftooh]

Allah knows best.