Musnad Ahmad 1153:2370

Hassan ibn Musa, Hashim, and Hussein ibn Muhammad narrated to us, they said: Shayban narrated to us, from Yahya, he said: Abu Salamah informed me—and Hashim said: from Abu Salamah—that Aisha—and Hashim said: from Aisha—informed him: "That the Messenger of Allah, may Allah bless him and grant him peace, used to pray the two rak'ahs between the call (adhan) and the iqamah of the morning prayer."