The description of the adhan and its place

Hisham bin Urwah narrates from his father (Urwah bin al-Zubayr) (may Allah have mercy on him) that "he used to call the words of the adhan twice each and say the words of the iqamah once each, that is, an odd number of times."
Imam al-Harith recorded this narration in his Musnad, and its chain is sahih (authentic). This is the authentic practice of Urwah bin al-Zubayr (may Allah have mercy on him), which is evidence for the Sunnah that the words of the adhan are said twice each and the words of the iqamah once each.

It is narrated from Ibn Abi Mulaykah, or from some other person of the people of Makkah, that "the Prophet (peace and blessings be upon him) ordered Sayyiduna Bilal (may Allah be pleased with him) to climb on top of the roof of the Ka'bah and give the adhan."
In the chain of this narration there is doubt and ambiguity about the name of the narrator; however, Sayyiduna Bilal's (may Allah be pleased with him) giving the adhan on the roof of the Ka'bah by order of the Messenger of Allah (peace and blessings be upon him) on the historic occasion of the Conquest of Makkah is established by other reliable and sahih hadith.