Sunan an-Nasa'i — The Book of the Adhan (The Call to Prayer) — Hadith No: 681
Translation
It was narrated that 'Abdullah bin Mughaffal said:"The Messenger of Allah (S.A.W) said: 'Between each two Adhans [1] there is a prayer, between each two Adhans there is a prayer, between each two Adhans there is a prayer, for whoever wants to do it." [1]Meaning, between the Adhan and Iqamah