Musnad Abu Ya'la al-Mawsili 150:169

'Abdullah ibn 'Amir ibn Zurarah al-Hadrami narrated to us, Yahya ibn Zakariya ibn Abi Za'idah narrated to us, from Muhammad ibn 'Amr, from Yahya ibn 'Abd al-Rahman ibn Hatib, from 'A'ishah: That the Messenger of Allah (may Allah bless him and grant him peace) married her when she was a girl of six years, and he consummated the marriage with her when she was a girl of nine years. Abu Bakr married her to him.