Sunan Abi Dawud Book 2, Hadith 121
This tradition has been narrated by Abu Ja’far, the mu’adhdhin of ‘Uryan mosque (at Kufah), from Abu al-Muthanna, the mu’adhdhin of masjid al-akbar (at kufah) on the authority of Ibn ‘Umar. The rest of the tradition was transmitted in a like manner.
The words of adhan were pronounced from the time of the Messenger of Allah (ﷺ) twice in pairs (i.e. four times) each, and the words of iqamah were pronounced once in pairs (twice each), except that the phrase "The time for prayer has come" would be pronounced twice. When we heard iqamah, we would perform ablution, and go out for prayer. Shu'bah said: I did not hear AbuJa'far narrating any other tradition except this one.
The Prophet (ﷺ) intended to do many things for calling (the people) to prayer, but he did not do any of them. Then Abdullah ibn Zayd was taught in a dream how to pronounce the call to prayer. He came to the Prophet (ﷺ) and informed him. He said: Teach it to Bilal. He then taught him, and Bilal made a call to prayer. Abdullah said: I saw it in a dream and I wished to pronounce it, but he (the Prophet) said: You should pronounce iqamah.