It is narrated from Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him) that he said: "O Messenger of Allah, make me the imam of my people." He (peace and blessings be upon him) said: "You are their imam; follow (the pace of) the weakest of them (in prayer), and appoint a mu'adhdhin who does not take a wage for his call to prayer (adhan)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8333