عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِذَا سَمِعَ الْمُنَادِي قَالَ: ((أَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ اللَّهِ))
It is narrated from Sayyidah Aisha Siddiqa (may Allah be pleased with her) that when the Messenger of Allah (peace and blessings be upon him) used to hear the caller to prayer (mu'adhdhin), he would say: "I bear witness that there is no god but Allah, and I bear witness that Muhammad is the Messenger of Allah."