Invoking Allah for Rain (Istisqaa)

Bukhari :: Book 2 :: Volume 17 :: Hadith 140

Narrated 'Abdullah bin Zaid Al-Ansari:

The Prophet went out towards the Musalla in order to offer the Istisqa' prayer and when he intended to invoke (Allah) or started invoking, he faced the Qibla and turned his cloak inside out.