Sahih Bukhari Volume 1, Book 11, Hadith Number 606

Narated By ‘Aun bin Abi Juhaifa : My father said, “I saw Allah’s Apostle at a place called Al-Abtah. Bilal came and informed him about the prayer and then came out with an Anza and planted it in front of Allah’s Apostle at Al-Abtah and pronounced the Iqama.”