Sunan an-Nasa'i, Volume 1, Book 7, Hadith 669 (DarusSalam) ⓘ

It was narrated that Abu Al-Muthanna, the Mu'adhdhin of the Jami' Masjid, said: "I asked Ibn 'Umar about the Adhan and he said: 'At the time of the Messenger of Allah, the phrases of the Adhan were recited twice and the phrases of Iqamah once, except that you should say (the phrase) Qad qamat is-salah (prayer is about to begin)twice. When we heard 'prayer is about to begin' we would perform Wudu' and go out to pray.'"

أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدِ بْنِ تَمِيمٍ، قَالَ حَدَّثَنَا حَجَّاجٌ، عَنْ شُعْبَةَ، قَالَ سَمِعْتُ أَبَا جَعْفَرٍ، مُؤَذِّنَ مَسْجِدِ الْعُرْيَانِ عَنْ أَبِي الْمُثَنَّى، مُؤَذِّنِ مَسْجِدِ الْجَامِعِ قَالَ سَأَلْتُ ابْنَ عُمَرَ عَنِ الأَذَانِ، فَقَالَ كَانَ الأَذَانُ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم مَثْنَى مَثْنَى وَالإِقَامَةُ مَرَّةً مَرَّةً إِلاَّ أَنَّكَ إِذَا قُلْتَ قَدْ قَامَتِ الصَّلاَةُ قَالَهَا مَرَّتَيْنِ فَإِذَا سَمِعْنَا قَدْ قَامَتِ الصَّلاَةُ تَوَضَّأْنَا ثُمَّ خَرَجْنَا إِلَى الصَّلاَةِ ‏.‏