Musnad Ahmad 27:792

Waki’ narrated to us, Shu’bah narrated to us, from al-Hakam and Salamah ibn Kuhayl, from Sa’id ibn Jubayr, from Ibn ‘Umar, that he performed them [the two prayers] with a single iqamah. He said: "This is how the Prophet, may Allah bless him and grant him peace, did for us in this place."