Sahih Bukhari Volume 4, Book 60, Hadith 3429

حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا شُعْبَةُ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، قَالَ لَمَّا نَزَلَتِ ‏{‏الَّذِينَ آمَنُوا وَلَمْ يَلْبِسُوا إِيمَانَهُمْ بِظُلْمٍ‏}‏ قَالَ أَصْحَابُ النَّبِيِّ صلى الله عليه وسلم أَيُّنَا لَمْ يَلْبِسْ إِيمَانَهُ بِظُلْمٍ فَنَزَلَتْ ‏{‏لاَ تُشْرِكْ بِاللَّهِ إِنَّ الشِّرْكَ لَظُلْمٌ عَظِيمٌ ‏}‏

Narrated By 'Abdullah : When the Verse: 'Those who believe and mix not their belief with wrong." was revealed, the companions of the Prophet said, "Who amongst us has not mixed his belief with wrong?" Then Allah revealed: "Join none in worship with Allah, Verily joining others in worship with Allah is a great wrong indeed."