question #1 Sahih al-Bukhari 612, Book 10, Hadith 10 : What is the significance of repeating the words of Adhan in Islam?

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 Messenger (ﷺ).)”