Sahih Bukhari
Invoking Allah for Rain (Istisqaa)
Volume: 002 / Book Number: 017 / Hadith Number: 139
Narrated Abbas bin Tamim from his uncle who said,
"The Prophet went out to the Musalla to offer the Istisqa' prayer, faced the Qibla and offered a two-Rakat prayer and turned his cloak inside out." Narrated Abu Bakr, "The Prophet put the right side of his cloak on his left side."