Musnad Ahmad 1153:1370

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Yazid al-Rishk, from Mu'adhah: That a woman asked 'Aishah: "Did the Messenger of Allah, peace and blessings of Allah be upon him, pray the Duha (forenoon) prayer?" She said: "Yes, four [rak'ahs], and he would increase whatever Allah willed."