Musnad Abu Ya'la al-Mawsili 149:102

Zakariya ibn Yahya al-Wasiti narrated to us, Hushaym narrated to us, from Mujalid, from al-Sha’bi, from ‘Aisha, who said: The Messenger of Allah (peace be upon him) commanded me to wash the face of Usama ibn Zayd one day while he was a young boy. She said: I had not given birth, and I did not know how to wash young boys. She said: So I took him and washed him in a way that was not quite right. She said: So he (the Prophet) took him and began to wash his face, saying: "You have been good to us, for had you been a girl, I would have adorned you and given you [gifts]."