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.
Hadith Referenceالفتح الربانی / كتاب الصلاة / 1277
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«أخرجه البخاري: 605، 607، ومسلم: 378 ، (انظر مسند أحمد ترقيم الرسالة:12024، 12971 ترقیم بيت الأفكار الدولية: 12024»
Brief Explanation
Benefits: … Reflecting on the above-mentioned narrations, two forms of adhan and iqamah have been described:
(1) The adhan with tarji‘ and, along with it, the iqamah with double phrases: Saying the adhan with tarji‘ is also Sunnah, in which "ashhadu an la ilaha illallah" and "ashhadu anna Muhammadan rasulullah" are each said four times. (Muslim)
When the Messenger of Allah sallallahu alayhi wa sallam taught Sayyiduna Abu Mahdhurah radi Allahu anhu the adhan with tarji‘, he also taught him the iqamah with double phrases. (Abu Dawud, Tirmidhi, Nasa’i, Ibn Majah)