Musnad Abu Ya'la al-Mawsili 150:76

Ja'far ibn Mihran narrated to us, 'Abd al-Warith narrated to us, from Yazid al-Rishk, from Mu'adhah, from 'Aishah: A woman asked 'Aishah about the continuous fasting (wisal) of the Messenger of Allah. She said, "Do you act as he acts? For indeed, his past and future sins have been forgiven, and his action was a supererogatory act." Then 'Aishah said, "As for me, by Allah, I have never fasted a night at all. Allah said: 'And complete the fast until the night' (Al-Baqarah)."