Sahih Bukhari
Call to Prayers (Adhaan)
Volume: 001 / Book Number: 011 / Hadith Number: 586
Narrated 'Isa bin Talha:
that he had heard Muawiya repeating the words of Adhan up to "Wa ash-hadu Anna Muhammadan Rasulul-lah (and I testify that Muhammad is Allah's Apostle.)"