Sunan Ibn Majah, Volume 1, Book 3, Hadith 730 (DarusSalam) ⓘ
It was narrated that Anas said: "Bilal was commanded to say the phrases of the Adhan twice and the phrases of the Iqamah once."
حَدَّثَنَا نَصْرُ بْنُ عَلِيٍّ الْجَهْضَمِيُّ، حَدَّثَنَا عُمَرُ بْنُ عَلِيٍّ، عَنْ خَالِدٍ الْحَذَّاءِ، عَنْ أَبِي قِلاَبَةَ، عَنْ أَنَسٍ، قَالَ أُمِرَ بِلاَلٌ أَنْ يَشْفَعَ، الأَذَانَ وَيُوتِرَ الإِقَامَةَ .
also referenced under: Hadith 730 (Reference) & Book 3, Hadith 25 (In-Book)