Sunan Ibn Majah, Chapter: Chapters Regarding Funerals

"While I was walking with the Messenger of Allah (saw) he said: 'O son of Khasasiyyah, why are you angry with Allah when you are walking with the Messenger of Allah?' I said: 'O Messenger of Allah! I am not angry with Allah at all. Allah has bestowed all good on me.' Then he passed by the graves of the Muslims and said: 'They have caught up with a great deal of good.' Then he passed by the graves of the idolaters and said: 'They died before a great deal of good came to them.' Then he turned and saw a man walking between the graves in his shows and he said: 'O you with the shows, take them off.'" Hasan