(15) باب الْقَوْلِ عِنْدَ الْمَطَرِ
It was narrated from 'Aishah that:
When it rained the Messenger of Allah would say: "Allahummaj'alhu Sayyiban nafi`a. (O Allah, make it beneficial rain)."
Reference: Sunan an-Nasa'i 1523
In-book reference: Book 17, Hadith 20
English translation: Vol. 2, Book 17, Hadith 1524