Mishkat al-Masabih #382

Ar-Rubaiyi‘ daughter of Mu'awwidh said that she saw the Prophet performing ablution, saying that he wiped his head front and back, his temples and his ears once. A version says that he performed ablution and inserted his two fingers in his ear-holes. Abu Dawud transmitted it. Tirmidhi transmitted the first version, and Ahmad and Ibn Majah the second.