Sahih Bukhari Volume 008, Book 075, Hadith Number 353.

Narated By Anas : While the Prophet was delivering a sermon on a Friday, a man stood up and said, "O Allah's Apostle! Invoke Allah to bless us with rain." (The Prophet invoked Allah for rain.) So, the sky became overcast and it started raining till one could hardly reach one's home. It kept on raining till the next Friday when the same man or another man got up and said (to the Prophet), "Invoke Allah to withhold the rain from us, for we have been drowned (with heavy rain)." The Prophet said, "O Allah! Let it rain around us and not on us." Then the clouds started dispersing around Medina and rain ceased to fall on the people of Medina.