The Prophet ﷺ used to repeat the testimony of faith along with the muezzins.
حدثنا وكيع حدثنا مجمع بن يحيى عن أبي أمامة بن سهل
أن النبي ﷺ كان يتشهد مع المؤذنين
No references are available.
Its isnad is sahih. Mujammi bin Yahya bin Yazid bin Jariyah is trustworthy, and his hadith appears in Muslim. The hadith also appears in Nasai, 24/2, no. 676, and it has already occurred at 16774.