Musnad Abu Ya'la al-Mawsili 150:282

Ahmad ibn Isa narrated to us, Bishr ibn Bakr narrated to us, al-Awza'i narrated to me, Yahya ibn Abi Kathir narrated to me, Abu Salamah narrated to me, 'Aishah narrated to me, she said: The Messenger of Allah (peace and blessings of Allah be upon him) used to pray two light rak'ahs between the call to prayer (adhan) and the iqamah.