Bulugh al-Maram #623

Narrated : When they experienced drought 'Umar bin al-Khattab (RA) used to seek rain by asking al-'Abbas bin 'Abdul Muttalib (RA) to supplicate Allah for rain. He ('Umar) would say: 'O Allah, we used to ask our Prophet (RA) to supplicate to You for rain, and You would give us rain. We are now asking our Prophet's uncle to supplicate to You for rain, so give us rain." They would then be given rain. .