Sunan an-Nasa'i 628
سنن النسائي#628SahihIt was narrated that Ibn 'Umar said:"At the time of the Messenger of Allah (S.A.W) the phrases of the Adhan were said twice and the phrases of the Iqamah were said once, except that you should say: 'Qad Qamatis-Salah, Qad Qamatis-Salah (prayer is about to begin, prayer is about to begin)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahHasan
Al-AlbaniHasan
Zubair Ali ZaiSahih
In-book reference: 7:3