Musannaf Ibn Abi Shayba 21:196

Hassan ibn Musa narrated to us, Laith ibn Sa'd narrated to us, from Khalid, from 'Uqayl, from Ibn Shihab, that he said: 'Urwah informed me, from 'Aishah, that the Messenger of Allah (may Allah bless him and grant him peace), when he took to his bed, would blow into his hands and recite the two *Mu'awwidhatayn* (Surah Al-Falaq and Surah An-Nas) into them. Then he would wipe his body with them.