Musnad Ahmad 30:2095

Ya'mar ibn Bishr narrated to us, Abdullah narrated to us, he said: Yahya ibn Ayyub informed us, he said: Abu Zur'ah narrated to us, from Abu Hurairah, he said: A man came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "What do you command me?" He said: "Be dutiful to your mother." Then he returned, and he said: "Be dutiful to your mother." Then he returned and said: "Be dutiful to your mother." Then he returned a fourth time, and he said: "Be dutiful to your father."