وَأَنا أَشْـهَدُ أَنْ لا إِلـهَ إِلاّ اللهُ وَحْـدَهُ لا شَـريكَ لَـهُ، وَأَنَّ مُحَمَّـداً عَبْـدُهُ وَرَسـولُه، رَضيـتُ بِاللهِ رَبَّـاً، وَبِمُحَمَّـدٍ رَسـولاً وَبِالإِسْلامِ دينَـاً
Wa-ana ashhadu an la ilaha illal-lahu wahdahu la shareeka lah, wa-anna Muhammadan AAabduhu warasooluh, radeetu billahi rabban wabimuhammadin rasoolan wabil-islami deena
Translation
And I too bear witness that none has the right to be worshipped except Allah, alone, without partner, and that Muhammad is His slave and Messenger. I am pleased with Allah as a Lord, and Muhammad as a Messenger and Islam as a religion.
When to recite
Recited after hearing the Muathin declare the Shahadah in the Adhan.
Source / Reference
Muslim 1/290