Invoking Allah for Rain (Istisqaa)

Bukhari :: Book 2 :: Volume 17 :: Hadith 146

Narrated Abu Huraira:

The Prophet said, "The Hour (Last Day) will not be established until (religious) knowledge will be taken away (by the death of religious learned men), earthquakes will be very frequent, time will pass quickly, afflictions will appear, murders will increase and money will overflow amongst you." (See Hadith No. 85 Vol 1).