Musnad Ahmad 27:841

'Abd al-Rahman narrated to us, Shu'bah narrated to us, from al-Hakam and Salamah ibn Kuhayl, from Sa'id ibn Jubayr, that he prayed the Maghrib [prayer] at Jam' [Muzdalifah] with one iqamah, and the 'Isha' [prayer] with one iqamah. Then he narrated from Ibn 'Umar that he did the same thing, and Ibn 'Umar narrated "that the Prophet, peace and blessings of Allah be upon him, did the same thing."