´Uthman bin Affan narrated that :` Allah's Messenger said: "Whoever attends Isha (prayer) in congregation, then he has (the reward as if he had) stood half of the night. And whoever prays Isha and Fajr in congregation, then he has (the reward as if he had) spend the entire night standing (in prayer)."
Hadith Referenceسنن ترمذي / كتاب الصلاة / 221
Hadith Gradingالألبانی:صحيح، صحيح أبي داود (564)
Hadith Takhrij«صحیح مسلم/المساجد 46 (656) ، سنن ابی داود/ الصلاة 48 (555) ، ( تحفة الأشراف : 9823) ، موطا امام مالک/ صلاة الجماعة 2 (7) ، مسند احمد (1/58، 68) (صحیح)»
Uthman bin Affan reported the Messenger of Allah (may peace be him) as saying; if anyone says the night prayer in congregation, he is like one who keeps vigil (in prayer) till midnight; and he who says both the night and dawn prayer in congregation is like one who keeps vigil (in prayer) the whole night.
Shaykh Umar Farooq Saeedi
555. Commentary: And whoever, after performing these prayers in congregation, also stands (in prayer) during the night, his rank will be exceedingly high.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 555