The Messenger of Allah ﷺ, whenever he saw rain, would say, "A beneficial downpour."
أن رسول الله ﷺ كان إذا رأى المطر قال: صيبا نافعا
Bukhari related it in Book of Rain-Seeking (1032) from Muhammad bin Muqatil Abu Hasan Marwazi, he said, Abdullah (that is, Ibn Mubarak) told us, Ubaydullah told us, from Nafi, from Qasim bin Muhammad, from Ayesha, and he mentioned it.His saying, "sayyiban," means pouring down heavily and streaming forth. Its root is with a waw, and the ya was substituted for it.