Anas reported that the Messenger of Allah (ﷺ) was not accustomed to raice his hands in any supplication he made except when praying for rain. (He would then raise [his hands] high enough) that the whiteness of his armpits became visible. 'Abd al-A'la said that (he was in doubt whether it was) the whiteness of his armpit or armpits

English translation · Sahih Muslim