Sahih Al Bukhari (562)

عن معاذ بن جبل أنه كان يصلي مع النبي صلى الله عليه وسلم ثم يرجع فيؤم قومه فصلى العشاء فقرأ بالبقرة فانصرف الرجل فكأن معاذا تناول منه فبلغ النبي صلى الله عليه وسلم فقال فتان فتان فتان ثلاث مرار أو قال فاتنا فاتنا فاتنا وأمره بسورتين من أوسط المفصل} قال عمرو لا أحفظهما.

‘Amr reported: Jabir ibn `Abdullah said, "Mu`adh ibn Jabal used to pray with the Prophet (peace be upon him) and then go to lead his people in prayer. Once he led the ‘Isha’ prayer and recited Surat "Al Baqrah." Somebody left the prayer and Mu`adh criticized him. The news reached the Prophet (peace be upon him) and he said to Mu‘adh, ‘You are putting the people to trial,’ and repeated it thrice (or said something similar) and ordered him to recite two medium Surahs of Mufassal." (‘Amr said that he had forgotten the names of those Surahs).