Repeat after Mu’adhdhin when pronouncing Adhan

Abu Sa`id Al-Khudri (May Allah be pleased with him) reported:

The Messenger of Allah (PBUH) said,

“When you hear the Mu’adhdhin (pronouncing the call to Salah), repeat after him what he says.”

[Al-Bukhari and Muslim]

Commentary:
This Hadith also tells us to repeat the words of Adhan when we hear it. But when he says “Hayya `alas-Salah” or “Hayya `alal-Falah” we must say “La hawla wa la quwwata illa billah.”

[Riyad-us-Saliheen – Hadith No.1038]