Musnad Ahmad 907:195

Yahya ibn Adam narrated to us, Isra'il narrated to us, from Simak, from Jabir ibn Samurah, who said: "The mu'adhdhin of the Messenger of Allah (may Allah bless him and grant him peace) would give the adhan, then he would wait, and he would not perform the iqamah until, when he saw that the Messenger of Allah (may Allah bless him and grant him peace) had come out, he would perform the iqamah for the prayer when he saw him."