Question 237: Salam, wanna ask if I am praying behind a Sunni imam then do i need to recite all in my own words or its same like as behind a Shia imam, any other difference?
Answer 237: Congregational Prayers is one of the most important recommended acts, and it is one of the greatest Islamic rites. Great emphasis has been laid on it in the narrations. It is recommended that obligatory prayers, especially the daily prayers, are performed in congregation, and more emphasis has been laid on congregational prayers for Fajr, Maghrib and Isha, and also for those who live in the neighborhood of a mosque, and are able to hear its Adhan.
There is no problem in attending Sunni congregational prayers; it is permissible and there are some reports according to which one who stands in the first row of their congregational prayers is like one who has offered his prayers standing behind the Holy Prophet (S) in the first row.
In any case, if possible, one should offer his prayers according to Shia way and if there is no need for Taqiyah (dissimulation) and one offers his prayers in Sunni way, he must repeat his prayers. Of course, there are some scholars who are of the view that if the conditions for practicing Taqiyah are not met, one must repeat his prayers under all circumstances.
Index: Some grand religious authorities have also replied to the same question. Their answers are as follows:
Grand Ayatollah Khamenei (may Allah grant him long life): In the said case, if using turbah is not in opposition with practicing Taqiyah, it is necessary to do Sajda on something which is allowed for prostration.
Grand Ayatollah Makarem Shirazi (may Allah grant him long life): If you are associating with them, there is no problem in offering prayers with them to protect yourself provided that they do not express enmity against Shia. However, doing Sajda on carpet is not allowed except where one practices Taqiyah in Sunni mosques.
Grand Ayatollah Noori Hamedani (may Allah grant him long life): If possible, one should do Sajda on things which are allowable for Sajdah but there is no problem in offering prayers behind a Sunni prayer leader and one is not, in the said case, required to repeat his prayers.
Grand Ayatollah Safi Golpaygani (may Allah grant him long life): If you are not in the state of Taqiyah, it is not sufficient and it would be necessary to repeat the prayers.
According to Khoei (ra) and Tabrizi (ra): “It is permissible to go to Sunni mosques and offer congregational prayers with Sunnis provided that one himself should engage in reciting Hamd and Surah.”
Tabrizi (ra): “If a person stands at a place in a Sunni mosque where part of the floor is covered with stone (slates), it is mandatory to do Sajda on the same stone.”
Sayyid Sistani (ha) says: It is permissible but you must recite Hamd and Surah yourself even though the recitation may be in low voice.
For further information in this regards, please refer to the following answer:
Index: The differences and similarities between Shia and Sunni, answer 187.
Index: Shia Believe Ahlus Sunnah are Muslim not Kafir!, answer 203.
Index: Saying Āmīn during prayer in validate the prayer, answer 017.
Index: Number of things which invalidate the prayer, answer 547.
Index: Miss a Sunni Imam in Ruku in congregational Prayer, answer 270.
Index: Qualification of an Imam of congregational prayers, answer 021.
 . Imam Khomeini, Tauzihul Masail (with annotation), vol.1, pg.767-768, Issue No.1399.
 . Kulayni, Muhammad bin Ya’qub, Al-Kafi, vol.3, p. 380, Dar al-Kutub al-Islamiyah, Tehran, fourth, 1407 A.H. The Arabic version of the tradition is as this: (عَنْ أَبِي عَبْدِ اللَّهِ ع قَالَ: مَنْ صَلَّى مَعَهُمْ فِي الصَّفِ الْأَوَّلِ كَانَ كَمَنْ صَلَّى خَلْفَ رَسُولِ اللَّهِ صلی الله علیه وآله و سلم)
 . This question has been sent to the offices of grand Ayatollah Khamenei, grand Ayatollah Makarem Shirazi, Grand Ayatollah Saafi Gulpaigani and Grand Ayatollah Noori Hamedani, may Allah grant them long life.
 . Khoei, Sayed Abul Qasim, Serat al-Najat (with connotation by Tabrizi), vol.3, pg.74, Al-Muntakhab Publication Office, qom, 1st edition, 1416 A.H.
 . Ibid.