Sahih al-Bukhari 605
صحيح البخاري#605SahihNarrated Anas:Bilal was ordered to repeat the wording of the Adhan for prayers twice, and to pronounce the wording of the Iqama once except "Qad-qamat-is-salat
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 10:3