It is narrated from Sayyiduna Mughirah bin Shu'bah (may Allah be pleased with him); he said: I asked the Prophet (peace and blessings be upon him) to make me the imam of my people, and he (peace and blessings be upon him) said: "Lead the prayer according to the weakest person, and do not appoint a mu'adhdhin who takes a wage for his call to prayer."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 18181