Bukhari 3710

From Sahih Bukhari (Hadith 3710):

Narrated Anas:Whenever there was drought, `Umar bin Al-Khattab used to ask Allah for rain through Al-`Abbas bin `Abdul Muttalib, saying, "O Allah! We used to request our Prophet to ask You for rain, and You would give us. Now we request the uncle of our Prophet to ask You for rain, so give us rain." And they would be given rain