The Muezzin of the Messenger of Allah (may Allah's peace and blessings be upon him) used to delay the Iqāmah until he would see the Messenger of Allah (may Allah's peace and blessings be upon him) coming out. On seeing him, he would pronounce the Iqāmah
Authentic hadithعن جابر بن سمرة رضي الله عنه قال: «كان مُؤَذِّنُ رسول الله -صلى الله عليه وسلَّم- يُمْهِلُ فلا يُقِيم، حتَّى إذا رأى رسول الله صلى الله عليه وسلم قد خرج أقام الصَّلاة حِين يَرَاه».
Jābir ibn Samurah (may Allah be pleased with him) reported: The Muezzin of the Messenger of Allah (may Allah's peace and blessings be upon him) used to delay the Iqāmah until he would see the Messenger of Allah (may Allah's peace and blessings be upon him) coming out. On seeing him, he would pronounce the Iqāmah.
Explanation
The Hadīth indicates that the Imām is the one who has the right to decide the timing of the Iqāmah, since the Muezzin used to delay it until the Prophet (may Allah's peace and blessings be upon him) would come out.
Source · Narrated by Muslim
From the Hadith Encyclopedia (hadeethenc.com).