Call to Prayers (Adhaan)

Bukhari :: Book 1 :: Volume 11 :: Hadith 603

Narrated Malik bin Huwairth:

Two men came to the Prophet with the intention of a journey. The Prophet said, "When (both of) you set out, pronounce Adhan and then Iqama and the oldest of you should lead the prayer."

Source materials are from the University of Southern California MSA site
Hadith eBooks converted from Imaan Star