´It 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."
Hadith ReferenceSunan an-Nasa'i / The Book of Praying for Rain (Al-Istisqa') / Hadith: 1514
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه