Musnad Ahmad 1153:1852

Hajjaj narrated to us, he said: Layth narrated to us, he said: Uqayl ibn Khalid narrated to me, from Ibn Shihab, he said: Urwah ibn al-Zubayr informed me, that Aisha, the wife of the Prophet, may God bless him and grant him peace, used to say: "The Messenger of God, may God bless him and grant him peace, did not perform the Duha prayer, and Aisha used to perform it." And she used to say: "Indeed, the Messenger of God, may God bless him and grant him peace, would abandon many deeds, fearing that the people would follow him in them, and thus they would become obligatory upon them."