Musnad Ahmad 792:33

Yahya ibn Sa'id narrated to us, Bahz narrated to us, my father narrated to me, from my grandfather, who said: I said, "O Messenger of Allah, whom should I treat with goodness?" He said, "Your mother." He said: I said, "Then whom?" He said, "Your mother." He said: I said, "Then whom?" He said, "Your mother, then your father, then the nearest, then the nearest."