question #3 Sahih Muslim 731b, Book 6, Hadith 135 : How does the recitation length in prayer affect the transition between sitting and standing positions?

The Messenger of Allah (ﷺ) used to pray while sitting (when he grew old) and he recited in this position and when the recitation equal to thirty or forty verses was left, he would then stand up and recite (for this duration) in a standing position and then bowed himself and then prostrated himself and did the same in the second rak’ah.