965
Musnad AhmedIt was narrated that ‘Abdur-Rahman bin Abi Laila said:
When "Ali bin Abi Talib (رضي الله عنه) heard the mu"addhin giving the adhan, he used to repeat after him. When he said, I bear witness that there is no god but Allah and I bear witness that Muhammad is the Messenger of Allah (ﷺ), "Ali (رضي الله عنه) would say: I bear witness that there is no god but Allah and I bear witness that Muhammad is the Messenger of Allah (ﷺ), and that those who deny Muhammad are the liars.
Reference: Musnad Ahmad 965
Arabic/English book : Book 5, Hadith 965
Arabic/English book : Book 5, Hadith 965