Narrated 'Abdullah:
"When (the following) was revealed: It is those who believe and confuse not their belief with Zulm (wrong) (6:82) - That bothered some Muslims, so they said: 'O Messenger of Allah! Which of us has not wronged himself?' He said: 'It is not that, it is only Shirk, have you not heard what Luqman said to his son: O my son! Do not commit Shirk with Allah. Verily Shirk is a tremendous Zulm (wrong) (31:13).'"
English reference: Vol. 5, Book 44, Hadith 3067
Arabic reference: Book 47, Hadith 3346