بُلُوغُ الْمَرَامِ
Bulugh al-Maram 196
The Book of Prayer
وَعَنْ مَالِكِ بْنِ الْحُوَيْرِثِ - رضى الله عنه - قَالَ : قَالَ لَنَا اَلنَّبِيُّ - صلى الله عليه وسلم -{ وَإِذَا حَضَرَتِ اَلصَّلَاةُ فَلْيُؤَذِّنْ لَكُمْ أَحَدُكُمْ . . . } اَلْحَدِيثَ أَخْرَجَهُ اَلسَّبْعَةُ . [1]
Narrated Malik bin al-Huwairith (RA): The Prophet (ﷺ) said to us, "When the time of Salat (prayer) comes, one of you should announce the Adhan." [Reported by as-Sab'ah].
Sunnah.com reference: Book 2, Hadith 58