Sahih Bukhari
Fighting for the Cause of Allah (Jihaad)
Volume: 004 / Book Number: 052 / Hadith Number: 317
Narrated Abdullah:
When the Prophet returned (from Jihad), he would say Takbir thrice and add, "We are returning, if Allah wishes, with repentance and worshipping and praising (our Lord) and prostrating ourselves before our Lord. Allah fulfilled His Promise and helped His Slave, and He Alone defeated the (infidel) clans."