Mu'tamirnarrated from his father, from Barakah, from Bashir binNahik, fromAbu Hurairah:
"The Prophet (ﷺ) supplicated for rain(raising hishands) until I saw or one could see the whiteness of hisarmpits."
English reference: Vol. 1, Book 5, Hadith 1271
Arabic reference: Book 5, Hadith 1330