Anas reported; Bilal was commanded to pronounce Adhan in double pairs and IQAMAH in single pairs. Hammam added in his version; “except IQAMAH”.  

أَنْ يَشْفَعَ الأَذَانَ وَيُوتِرَ الإِقَامَةَ زَادَ حَمَّادٌ فِي حَدِيثِهِ إِلاَّ الإِقَامَةَ  

I narrated this tradition to Ayyub who said: “Except IQAMAH”.  

إِلاَّ الإِقَامَةَ  

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.  

إِنَّمَا كَانَ الأَذَانُ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ مَرَّتَيْنِ مَرَّتَيْنِ وَالإِقَامَةُ مَرَّةً مَرَّةً غَيْرَ أَنَّهُ يَقُولُ قَدْ قَامَتِ الصَّلاَةُ قَدْ قَامَتِ الصَّلاَةُ فَإِذَا سَمِعْنَا الإِقَامَةَ تَوَضَّأْنَا ثُمَّ خَرَجْنَا إِلَى الصَّلاَةِ قَالَ شُعْبَةُ وَلَمْ أَسْمَعْ مِنْ أَبِي جَعْفَرٍ غَيْرَ هَذَا الْحَدِيثِ  

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.  

سَمِعْتُ أَبَا الْمُثَنَّى مُؤَذِّنَ مَسْجِدِ الأَكْبَرِ يَقُولُ سَمِعْتُ ابْنَ عُمَرَ وَسَاقَ الْحَدِيثَ