Nafi reported that whenever it rained, the Messenger of Allah ﷺ would say, "O Allah, make it a beneficial downpour."
أخبرنا محمد بن منصور قال حدثنا سفيان عن مسعر عن المقدام بن شريح عن أبيه
أن رسول الله ﷺ كان إذا أمطر قال اللهم اجعله صيبا نافعا
No references are available.
[Its chain of transmission is sahih] Humaydi narrated it (hadith no. 71 of the Zahiriyyah edition per my verification) from Sufyan bin Uyayna, who said, Masaar narrated to us the same. It is also found in Kubra, hadith no. 1828. Abu Dawud narrated it, hadith no. 5099, as did Ibn Majah, hadith no. 3889, and others, from the hadith of Miqdam with the same content.