It is narrated from Sayyiduna Abu Mahdhurah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Those who give the adhan are the trustees of the Muslims over (the times of) their iftar and their suhur."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6713