مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4212
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah (رضي الله عنه) said: When this verse was revealed, “It is those who believe (in the Oneness of Allah and worship none but Him Alone) and confuse not their Belief with Zulm (wrong)" (al-An'am 6:82), it was very hard on the Companions of the Messenger of Allah (ﷺ) and they said: Who among us does not does wrong? The Messenger of Allah (ﷺ) said: "It is not as you think; rather it is as Luqman said to his son: "O my son! Join not in worship others with Allah. Verily, joining others in worship with Allah is a great Zulm (wrong) indeed' (Luqmaan 31:13)?"
Musnad Ahmad 4240lts isnad is saheeh, al-Bukhari (6937) and Muslin (124)]