Abdur-Rahman bin Sa'd bin 'Ammar bin Sa'd narrated (from his great-grandfather of the Messenger of Allah) that:In the Adhan of Bilal, the phrases were two by two, and in his Iqamah they were said once
Hadith No. 731
Sunan Ibn Majah
Gradings:
Al-Albani:
Sahih
Muhammad Fouad Abd al-Baqi:
Sahih
Shuaib Al Arnaut:
Sahih Lighairihi
Zubair Ali Zai:
Daif