A Forgotten Sunnah: When the Mu’adhin says the Two Testimonies of Faith (in the Adhan), the listener says: “And I (too), and I (too)”
عَنْ عَائِشَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا سَمِعَ الْمُؤَذِّنَ يَتَشَهَّدُ قَالَ “ وَأَنَا وَأَنَا
‘A’ishah said that when the Messenger of Allah (ﷺ) heard the Mu’adhain uttering the testimonties, he would say:“And I too, and I too”.
Shaikh al-Albani (may Allah have mercy upon him) said: “It is permissible to restrict oneself, sometimes, with the statement: “And I too, and I too” when the Mu’adhin says: “I bear witness that there is no Deity worthy of worship except Allah and that Muhammad is the Messenger of Allah”. Likewise, the Messenger of Allah (ﷺ) used to do this” [ath-Thamr ul-Mustadaab (1/184)]
Faisal bin Abdul Qaadir bin Hassan