Ziyad bin 'Alaqa زياد بن علاقة · The Book of Fighting [The Prohibition of Bloodshed]

"I heard Anas say: 'The Messenger of Allah said: The major sins are: Associating others with Allah (Shirk), disobeying one's parents, killing a soul (murder) and speaking falsely.'"

The Prophet said: "The major sins are: Associating others with Allah, disobeying parents, killing a soul (murder) and swearing a false oath knowingly."

His father - who was one of the Companions of the Prophet - told him: "A man said: 'O Messenger of Allah, what are the major sins?' He said: 'They are seven; the most grievous of which are associating others with Allah, killing a soul unlawfully and fleeing (from the battlefield) on the day of the march.'" It is abridged.

"I said: 'O Messenger of Allah, which sin is the most grievous?' He said: 'Setting up a rival to Allah while it is He that has created you.' I said: 'Then what?' He said: 'Killing your child for fear that he may eat with you.' I said: 'Then what?' He said: 'Committing adultery with your neighbor's wife.'"