Prayer › Supplications related to the athan (the call to prayer)
Dua during the adhan — affirming the testimony
Immediately following the declaration of faith called by the Mu'adh-dhin, one says:
وَأَنَا أَشْـهَدُ أَنْ لَا إِلَـهَ إِلاَّ اللهُ وَحْـدَهُ لَا شَـرِيْكَ لَـه ، وَأَنَّ محَمّـداً عَبْـدُهُ وَرَسُـوْلُهُ ، رَضِيْـتُ بِاللهِ رَبَّـاً ، وَبِمُحَمَّـدٍ رَسُـوْلاً وَبِالإِسْلَامِ دِيْنَـاً
Wa ana ash-hadu an la ilaha illallahu wahdahu la sharika lahu, wa anna Muhammadan abduhu wa rasuluhu, radhitu billahi rabban, wa bi-Muhammadin rasulan, wa bil-islami dina
Translation
And I too bear witness that none has the right to be worshipped except Allah, alone, without partner, and that Mohammed is His salve and Messenger. I am pleased with Allah as a Lord, and Mohammed as a Messenger and Islam as a religion.
When to recite
During the adhan, upon the testimony of faith.
Source / Reference
Hisnul Muslim 23