(60) باب إِذَا طَوَّلَ الإِمَامُ وَكَانَ لِلرَّجُلِ حَاجَةٌ فَخَرَجَ فَصَلَّى
Narrated `Amr:
Jabir bin `Abdullah said, "Mu`adh bin Jabal used to pray with the Prophet (ﷺ) and then go to lead his people in prayer Once he led the `Isha' prayer and recited Surat "Al-Baqara." Somebody left the prayer and Mu`adh criticized him. The news reached the Prophet (ﷺ) 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 Suras of Mufassal." (`Amr said that he had forgotten the names of those Suras).
Reference: Sahih al-Bukhari 701
In-book reference: Book 10, Hadith 96
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 11, Hadith 669