Ayesha said, "Whenever the Messenger of Allah ﷺ heard the caller to prayer, he would say, 'I bear witness that there is no god but Allah, and I bear witness that Muhammad is the Messenger of Allah.'"
قال حدثنا عفان قال حدثنا عبد الواحد بن زياد قال حدثني
قالت عائشة كان رسول الله ﷺ إذا سمع المنادي قال أشهد أن لا إله إلا الله وأشهد أن محمدا رسول الله
Its isnad is sahih. Amr bin Maymun bin Mihran is a well-known trustworthy narrator, and his hadith is found in the works of the group of major compilers. The hadith has already appeared at 23756.