It was narrated that Ibn 'Umar said:
"At the time of the Messenger of Allah (ﷺ) the phrases of the Adhan were said twice and the phrases of the Iqamah were said once, except that you should I say: 'Qad Qamatis-Salah, Qad Qamatis-Salah (prayer is about to begin, prayer is about to begin).'" (DE)
English reference (DE): Vol. 1, Book 7, Hadith 629 (DE)
Arabic reference (DE): Book 7, Hadith 635 (DE)