DU'A UPON HEARING THE ADHAN
Allah SWT has made Islam a very beautiful and easy-to-follow religion for all Muslims. Salah is one of the most essential pillars of Islam. It is mandatory upon every Muslim to perform Namaz five times a day.
Therefore, to remind Muslims of the specific time of prayer, it is the duty of the muezzin to give Adhan – call to prayer. It is said that every person who utters the sentences of the Adhan will find their heart full of divine grace and purity.
Repeat what the Mu'adhdhin (The call Maker) says, except for when he says:
حي على الصلاة وحي على الفلاح
Hayya'alas-Salah (Come to the prayer) and Hayya'alal-Falaah (Come to the success). You are to reply to those by saying:
لا حول ولا قوة الا بالله
La-haula walaa quwwata'illaa billaah.
There is no power and might expect from Allah.
(Bukhari & Muslim)