613 - It was narrated from Mu‘awiyah ibn Abi Sufyan (may Allah be pleased with him) that when he [the mu’adhdhin] said Hayya ‘ala al-salah, he said: La hawla wa la quwwata illa Billah; and he said: This is what we heard your Prophet (blessings and peace of Allah be upon him) saying..

Commentary : The adhan and the mu’adhdhin have many virtues and are matters of high status before Allah (may He be exalted). In order that the listener will not be deprived of this reward, he is instructed to repeat after the mu’adhdhin. Our Prophet (blessings and peace of Allah be upon him) has taught us how to repeat the adhan after the mu’adhdhin. This hadith explains some of that, as the Tabi‘i Yahya ibn Abi Kathir narrates from Mu‘awiyah ibn Abi Sufyan (may Allah be pleased with him) that when he heard the mu’adhdhin say Hayya ‘ala al-salah, Mu‘awiyah said: La hawla wa la quwwata illa Billah, and stated that he did that as he had heard it from the Prophet (blessings and peace of Allah be upon him). Hence this is the Sunnah of repeating after the mu’adhdhin and responding to his words in the case of the two phrases “Hayya ‘ala al-salah” and “Hayya ‘ala al-falah.” When the mu’adhdhin says these two phrases, the listener should respond by saying: La hawla wa la quwwata illa Billah. That is because in the case of phrases other than “Hayya ‘ala al-salah” and “Hayya ‘ala al-falah”, both the listener and the mu’adhdhin share in the reward – such as when saying “Allahu akbar” and “La ilaha illa Allah”, and the other phrases of the adhan – because they are a kind of dhikr. However, with regard to the phrases “Hayya ‘ala al-salah” and “Hayya ‘ala al-falah”, the aim is to call the people to prayer, because these phrases effectively mean: Come to prayer, come to strive. This is what the mu’adhdhin is doing when he says these words. Therefore Allah compensates the listener for what he misses out on of the reward for that, with the reward for saying La hawla wa la quwwata illa Billah. And it was said that the listener says La hawla wa la quwwata illa Billah at this point because the meaning of the phrases “Hayya ‘ala al-salah” and “Hayya ‘ala al-falah” is: Come with your devotion and clean heart to guidance in the immediate moment, and come to great success later on. So it is appropriate for him to say: This is a momentous matter that I cannot do with the weakness that is inherent in me, unless Allah helps me with His power and strength.
This hadith highlights Mu‘awiyah’s knowledge and keenness to follow the Sunnah of the Prophet (blessings and peace of Allah be upon him)..