Musnad Ahmad 907:44

Humaid ibn Abd al-Rahman narrated to us, Zuhayr narrated to us, from Simak, from Jabir ibn Samurah, who said: "Bilal used to call the Adhan when the sun passed its zenith, not failing to do so. Then he would not perform the Iqamah until the Prophet, peace and blessings of Allah be upon him, came out." He said: "So when he came out, he would perform the Iqamah the moment he saw him."