Hadithcore
Mishkat al-Masabih, 677

‘A’isha said that when the Prophet (ﷺ) heard the <i>mu’adhdhin</i> uttering the testimony, he said, “I too, I too.” Abu Dawud transmitted it.

وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا سَمِعَ الْمُؤَذِّنَ يَتَشَهَّدُ قَالَ: «وَأَنَا وَأَنَا» . رَوَاهُ أَبُو دَاوُد

References1 variant
In-Book Reference
Book 4, Hadith 109