Narrated Malik bin Huwairith: Prophet said (to two persons), "Whenever the prayer time becomes due, you should pronounce Adhan and then Iqama and the older of you should lead the prayer."
Hadith ReferenceSahih Bukhari / The Book of Adhan / Hadith: 658
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة