"Allah's Messenger would say each phrase of the call (for prayer) two times, for the Adhan and the Iqamah."
Jami` at-Tirmidhi Book 2, Hadith 46
← Previous Hadith "Bilal was ordered to make the phrases of the Adhan even, and the phrases of the Iqamah odd."

Jami` at-Tirmidhi Book 2, Hadith 45 Next Hadith → "Allah's Messenger said to Bilal: "O Bilal! When you call the Adhan then do so deliberately and slowly, and when you call the Iqamah then be quick. Allow enough time between your Adhan and Iqamah for the person eating to finish what he is eating, the person drinking to finish what he is drinking, and the one who needs time to relive himself, and do not stand until you see me."

Jami` at-Tirmidhi Book 2, Hadith 47