Narrated 'Uthman bin Abul-'Aas (RA): He said, "O Messenger of Allah, appointment as the Imam (leader) of my people (in prayers). He (ﷺ) said: "You are their Imam, but you should follow (observe the strength of) the weakest among them and appoint a Mu'adhdhin who does not charge for the call of Adhan." [Reported by al-Khamsah, at-Tirmidhi graded it Hasan (good) and al-Hakim graded it Sahih (authentic)].