Sahih al-Bukhari 6106
Good Manners and Form (Al-Adab)
Whoever does not consider as Kafir the person who says that...
Narrated Jabir bin `Abdullah: Mu`adh bin Jabal used to pray with the Prophet (ﷺ) and then go to lead his people in prayer. Once he led the people in prayer and recited Surat-al-Baqara. A man left (the row of the praying people) and offered (light) prayer (separately) and went away. When Mu`adh came to know about it, he said. "He (that man) is a hypocrite." Later that man heard what Mu`adh said about him, so he came to the Prophet (ﷺ) and said, "O Allah's Messenger (ﷺ) ! We are people who work with our own hands and irrigate (our farms) with our camels. Last night Mu`adh led us in the (night) prayer and he recited Sura-al-Baqara, so I offered my prayer separately, and because of that, he accused me of being a hypocrite." The Prophet (ﷺ) called Mu`adh and said thrice, "O Mu`adh! You are putting the people to trials? Recite 'Washshamsi wad-uhaha' (91) or'Sabbih isma Rabbi ka-l-A'la' (87) or the like."