Jabir b. Samurah said:
Bilal would call the Adhan, then he used come to wait. When he would see that the prophet ﷺ had come out (of his house), he would pronounce the iqama.

حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا شَبَابَةُ، عَنْ إِسْرَائِيلَ، عَنْ سِمَاكٍ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ كَانَ بِلاَلٌ يُؤَذِّنُ ثُمَّ يُمْهِلُ فَإِذَا رَأَى النَّبِيَّ ﷺ قَدْ خَرَجَ أَقَامَ الصَّلاَةَ .