What did Prophet Muhammad (saw) say to Mu'adh when he was informed about the man who said prayer separately from the congregation?
 Jabir reported:                      'Mu'adh b jabal al-Ansari led his companions in the night prayer and prolonged it for them. A person amongst us said prayer (after having separated himself from the congregation). Mu'adh was informed of this, and he remarked that he wasa hypocrite. When it (the remark) was conveyed to the man, he went to the Messenger of Allah (may peace be upon him) and informed him of what Mu'adh had said. Upon this the Apostle of Allah (may peace be upon him) said to him: Mu'adh, do you want to become a person putting (people) to trial? When you lead people in prayer, recite:" By the Sun and its morning brightness" (Surah xci.)," Glorify the name of thy most high Lord" (Surah lxxxvi.) and" Read in the name of Lord" (Surah xcvi.), and" By the night when it spreads" (Surah xcii.).