Umm al-Mu'minin Aisha Siddiqa (may Allah be pleased with her) says: I did not see the Messenger of Allah (peace and blessings of Allah be upon him) reciting (Qur'an) while sitting during the night prayer. But when he became old, he would recite while sitting, and when about thirty or forty verses of the surah remained, he would stand up and recite, then bow (ruku).