Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1426
Malik b Huwairith reported: I came to the Apostle of Allah (may peace be upon him) along with a companion of mine, and when we intended to return from him, he said: When there is time for prayer, announce prayer, pronounce Iqama, and the oldest amongst you should lead the prayer.