عَنْ أَنَسِ بْنِ مَالِكٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: أُمِرَ بِلَالٌ أَنْ يَشْفَعَ الْأَذَانَ وَيُوْتِرَ الْإِقَامَةَ
Sayyiduna Anas bin Malik (may Allah be pleased with him) says: Sayyiduna Bilal (may Allah be pleased with him) was commanded to say the words of the adhan twice each, and to say the words of the iqamah once each.