´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)»