Hisn al-Muslim

Repeat what the Mu'adh-dhin says, except for when he says: Hayya 'alas-Salāh (hasten to the prayer) and Hayya 'alal-Falāh (hasten to salvation). Here you should say: Lā ḥawla wa lā quwwata 'illā billāh. There is no might and no power except by Allah. Reference: Al-Bukhari 1/152, Muslim 1/288.