Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: If we wished to see the Prophet Muhammad (peace and blessings be upon him) performing voluntary prayers at night, we would see him performing them, and if we wished to see him sleeping at night, we would see him sleeping as well.
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2617
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: خ (1972 و 1973).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرطهما