Allah's Messenger said: "They said: 'O Messenger of Allah, whom should I treat kindly?' He said: 'Your mother.' He said: 'Then who?' He said :'Your mother." He said: 'Then who?' He said: 'Your father'. He said : 'Then who?' He said: 'The next closest and the next closest.'"
Sunan Ibn Majah Book 33, Hadith 2