Musnad Ahmad 1153:1383

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Sulayman, he said: I heard Abu al-Duha narrating from Masruq, from 'Aishah, that she said: "The Messenger of Allah, peace and blessings of Allah be upon him, gave his wives the choice. Was that considered a divorce?"