What is the example that `Umar bin Al-Khattab used to turn to Prophet Muhammad (peace be upon him) for rain?
 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."