بُلُوغُ الْمَرَامِ
Bulugh al-Maram 181
The Book of Prayer
وَعَنْ أَنَسِ]بْنِ مَالِكٍ] - رضى الله عنه - قَالَ: { أُمِرَ بِلَالٌ أَنْ يَشْفَعَ اَلْآذَانَ, وَيُوتِرَ اَلْإِقَامَةَ, إِلَّا اَلْإِقَامَةَ, يَعْنِي قَوْلَهُ: قَدْ قَامَتِ اَلصَّلَاةُ } مُتَّفَقٌ عَلَيْهِ, وَلَمْ يَذْكُرْ مُسْلِمٌ اَلِاسْتِثْنَاءَ [1] .
Narrated Anas (RA): Bilal was commanded to announce the Adhan (each phrase) twice and the Iqamah (each phrase) once except "The prayer stood ready to begin" (to be pronounced twice). [Agreed upon; but Muslim did not mentioned the exception].
Sunnah.com reference: Book 2, Hadith 37