It was narrated that 'Abdullah said: "I said: 'O Messenger of Allah, which sin is most grievous?' He said: 'Setting up a rival to Allah while it is He that created you.' I said: 'Then what?' He said: 'Killing your child so that he will not eat with you.' I said: 'Then what?' He said: 'Committing adultery with your neighbor's wife.'"