Musannaf Ibn Abi Shayba 1:1130

Waki’ narrated to us, from Sufyan, from Mansur, from Musa ibn ‘Abd Allah ibn Yazid, from the freed slave of ‘A’ishah, from ‘A’ishah, that she said: I never looked at, or I never saw, the private part of the Messenger of Allah, may Allah bless him and grant him peace, at all.