Saib bin Yazid narrates: In the time of the Prophet (peace be upon him), Sayyiduna Abu Bakr (may Allah be pleased with him), and Sayyiduna Umar (may Allah be pleased with him), the words of the adhan were said twice (that is, on the day of Jumu'ah there was one adhan and one iqamah), until the era of Sayyiduna Uthman (may Allah be pleased with him) came and the people increased in number, so he instructed the mu'adhdhin to give a second adhan at the place of Zawra' (on the day of Jumu'ah).
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 1673
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صحيح أبي داود» (998): خ.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط البخاري، رجاله رجال الشيخين غير مسدد، فإنه من رجال البخاري.