Sunan an-Nasa'i 1513
سنن النسائي#1513SahihIt was narrated that Anas said:"The Messenger of Allah (ﷺ) did not raise his hands during any supplication except when praying for rain, when he used to raise his hands so high that the whiteness of his armpits could be seen
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 - Agreed Upon
In-book reference: 17:10