Musannaf Ibn Abi Shayba 3:6314

'Affan narrated to us, he said: 'Abd al-Wahid ibn Ziyad narrated to us, from al-Hasan ibn 'Ubayd Allah, he said: Ibrahim narrated to us, from al-Aswad, from 'A'ishah, she said: The Messenger of Allah (may Allah bless him and grant him peace) used to exert himself in the ten [days] with an exertion he did not exert in other than it.