Musnad Ahmad 1060:76

Ahmad ibn al-Hajjaj narrated to us, Abdullah ibn al-Mubarak narrated to us, Sufyan informed us, from Jabir, from Adi ibn Thabit, from Abdullah ibn Yazid al-Khatmi, from Abu Ayyub al-Ansari: From the Prophet, may Allah bless him and grant him peace, that he used to pray Maghrib and Isha with an iqamah.