Sunan Ibn Majah 729
سنن ابن ماجه#729SahihIt was narrated that Anas bin Malik said:"They looked for something by means of which they could call out informing of (the time of) the prayer. Then Bilal was commanded to say the phrases of the Adhan twice and the phrases of the Iqamah once
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 3:24