Musnad Ahmad 1153:1843

Hajjaj narrated to us, he said: Shareek informed us, from al-Abbas ibn Dhureeh, from al-Bahee, from Aisha, that Usama ibn Zayd stumbled at the threshold—or the step—of the door, and he was wounded on his forehead. The Messenger of Allah, peace and blessings of Allah be upon him, said to me: "Remove the harm from him"—or "Put the harm away from him." She said: So I felt squeamish about it. She said: Then the Messenger of Allah, peace and blessings of Allah be upon him, began to suck it and then spit it out. And the Messenger of Allah, peace and blessings of Allah be upon him, said: "If Usama were a girl, I would have clothed her and adorned her until I married her off."