Musnad Ahmad 1153:1269

Hammad narrated to us, Hisham informed us, from Hisham ibn Urwah, he said: I heard Urwah narrating from Aisha, she said: "I used to perfume the Messenger of Allah, peace and blessings of Allah be upon him, with the best [scent] I could find before he entered into the state of Ihram, then he would enter into the state of Ihram."