Sayyidah Aisha Siddiqa (may Allah be pleased with her) narrates: The Prophet Muhammad (peace be upon him) would not recite while sitting in the voluntary night prayer until, when he became older, he began to recite while sitting. And when there remained thirty or forty verses of a surah, he would stand and recite them, then go into bowing (ruku).
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2633
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - انظر ما قبله.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين