(3) باب السُّنَّةِ فِي الأَذَانِ
It was narrated that Jabir bin Samurah said:
"Bilal did not delay the Adhan from its proper time, but he sometimes delayed the Iqamah a little."
Reference: Sunan Ibn Majah 713
In-book reference: Book 3, Hadith 8
English translation: Vol. 1, Book 3, Hadith 713