Offering the Maghrib Prayer behind an Imam offering the `Isha' Prayer
It is obligatory upon a person
who offers Maghrib Prayer behind an Imam who is offering `Isha' Prayer to wait for him in the third Rak`ah until he offers the fourth Rak`ah and ends Salah. He may also intend to separate from him in the third Rak`ah by sitting, making Tashahud and ending Salah. If he completes four Rak`ahs with the Imam forgetfully and did not change his intention to `Isha' Prayer, his Salah will be valid but he should offer Sujud Al-Sahw (Prostration of Forgetfulness) if he knew this before or after Salam (Final salutation of ending Salah) before the passage of a long time.
Q 2: What is the ruling on a person who entered the Masjid to offer Maghrib (Sunset) Prayer and found a congregation offering Salah? He joined them and afterwards, he realized that he caught up with the Imam in (Part No. 6; Page No. 245) the second Rak`ah of `Isha' (Night) Prayer. By doing this, he offered one Rak`ah then sat for the first Tashahud then offered two Rak`ahs with the Imam; is his Salah of Maghrib valid? Is it permissible for him to offer `Isha' Prayer individually because the people at the Masjid (mosque) had already offered `Isha' Prayer combined with Maghrib?
a latecomer offers Maghrib Prayer behind an Imam who is offering `Isha' Prayer, his Salah is valid and it is permissible for him to offer `Isha' afterwards because this excuse is made for him as well as the people of the Masjid.
Q 3: When a person enters a Masjid and finds a congregation offering Salat-ul-Tarawih (Voluntary night Salah performed in Ramadan) and he had not performed `Isha' (Night) Prayer, can he join them with the intention of offering `Isha' and then complete the remaining two Rak`ahs?
It is permissible to offer `Isha' Prayer behind an Imam
who is offering Salat-ul-Tarawih. When the Imam ends his Salah, the latecomer has to complete `Isha' Prayer. It was reported on the authority of Mu`adh (may Allah be pleased with him) that he used to offer `Isha' Prayer with the Prophet (peace be upon him) then go back to his people to lead them in that Salah, as it is supererogatory for him and obligatory for them. The Prophet (peace be upon him) approved of his action. The Prophet (peace be upon him) offered other types of Salah in which he led a group of people in two Rak`ahs and led another group in another two Rak`ahs which was supererogatory for him and obligatory for them.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.