Musannaf Ibn Abi Shaybah

Hazrat Ali (may Allah be pleased with him) used to say that both the Adhan and the Iqamah should be said twice each. Hazrat Ali (may Allah be pleased with him) once scolded a mu’adhdhin who said the Iqamah once, and said to him, "May Allah keep you away from His mercy, why did you not say the Iqamah twice?"

Hazrat Ubaid says that Hazrat Salamah bin Akwa’ used to say the Iqamah twice.

Hazrat Abdur Rahman bin Abi Laila narrates that Hazrat Abdullah bin Zaid Ansari, who was the muezzin of the Messenger of Allah (peace and blessings be upon him), used to say the adhan and iqamah twice each.

Hazrat Abu Alia says that when you say the Iqamah, say it twice.

Ibrahim says: Do not omit saying the iqamah twice.

Hazrat Abu Ishaq states that the students of Hazrat Ali (may Allah be pleased with him) and Hazrat Abdullah used to say the adhan and iqamah twice each.

Ibrahim narrates that Hazrat Bilal used to say the adhan and iqamah twice each.