Sunan an-Nasa'i 1650
سنن النسائي#1650SahihIt was narrated that Aishah said:"The Messenger of Allah (ﷺ) used to recite sitting, and when he wanted to bow he would stand up for as long as it takes a person to recite forty verses
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 20:53