Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"A Bedouin came to the Prophet (saw) and said: 'O Messenger of Allah, I have come to you from people who have no place to graze their flocks and even their male camels have become weak. He mounted the pulpit and praised Allah, then he said: 'O Allah, send upon us all abundant, wholesome rain, productive and plentiful, sooner rather than later.' Then the rain came down, and no one came to him from any direction but they said: 'We have been revived.'" Sahih