question #2 Sahih Muslim 731a, Book 6, Hadith 134 : What is the significance of standing up to recite the remaining verses during night prayer?

I did not see the Messenger of Allah (ﷺ) reciting (the Qur’an) in the night prayer in a sitting position, till he grew old and then he recited (it) in a sitting position, but when thirty or forty verses were left out of the Surah, he would then stand up, recite them and then bowed.