Musnad Ahmad 1153:98

Ishaq ibn Yusuf narrated to us, he said: Sufyan informed us, from al-Hasan ibn Ubayd Allah, from Ibrahim, from al-Aswad, from Aisha, who said: "It is as if I am looking at the glistening of musk on the head of the Messenger of Allah, may Allah bless him and grant him peace, while he was in the state of ihram."