The sin of the person who ascribes partners in worship to Allah
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ قَالَ لَمَّا نَزَلَتْ هَذِهِ الآيَةُ {الَّذِينَ آمَنُوا وَلَمْ يَلْبِسُوا إِيمَانَهُمْ بِظُلْمٍ} شَقَّ ذَلِكَ عَلَى أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم وَقَالُوا أَيُّنَا لَمْ يَلْبِسْ إِيمَانَهُ بِظُلْمٍ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّهُ لَيْسَ بِذَاكَ، أَلاَ تَسْمَعُونَ إِلَى قَوْلِ لُقْمَانَ {إِنَّ الشِّرْكَ لَظُلْمٌ عَظِيمٌ} ".
Narrated `Abdullah: When the Verse: 'It is those who believe and confuse not their belief with wrong (i.e., worshipping others besides Allah): (6.82) was revealed, it became very hard on the companions of the Prophet (ﷺ) and they said, "Who among us has not confused his belief with wrong (oppression)?" On that, Allah's Apostle said, "This is not meant (by the Verse). Don't you listen to Luqman's statement: 'Verily! Joining others in worship with Allah is a great wrong indeed.' (31.13)