Abdur Rahman bin Abu Amrah narrates: Sayyiduna Uthman Ghani (may Allah be pleased with him) entered the mosque after the Maghrib prayer and sat alone. I came and sat with him, so he said: O my nephew, I heard the Prophet Muhammad (peace and blessings be upon him) say: "Whoever performs the Isha prayer in congregation, it is as if he has spent half the night in voluntary prayers, and whoever also performs the Fajr prayer in congregation, it is as if he has spent the entire night in voluntary prayers."
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2060
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: م - انظر ما قبله.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط مسلم.