“Mu’adh bin Jabal Al-Ansari led his companions in the ‘Isha’ prayer and he made it long. A man among us went away and prayed by himself. Mu’adh was told about that and he said: ‘He is a hypocrite.’ When the man heard about that, he went to the Messenger of Allah (ﷺ) and told him what Mu’adh had said to him. The Prophet (ﷺ) said: ‘Do you want to be a cause of Fitnah (trial, tribulation), O Mu’adh? When you lead the people in prayer, recite “By the sun and its brightness,” and “Glorify the Name of your Lord the Most High,” and “By the night as it envelopes,” and “Recite in the Name of your Lord.’”
Sunan Ibn Majah Book 5, Hadith 184