Ahmed bin al-Hasan bin Junaydab أحمد بن الحسن بن جنيدب · The Book on Salat (Prayer)

"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."