Musnad Ahmad 1153:1486

'Ali narrated to us, Sufyan ibn Husayn informed me, from al-Zuhri, from 'Urwah ibn al-Zubayr, from 'Aishah, she said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Every condition that is not in the Book of Allah, the Mighty and Majestic, is rejected, even if they stipulate it a hundred times."