Sahih Bukhari
Invoking Allah for Rain (Istisqaa)
Volume: 002 / Book Number: 017 / Hadith Number: 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.