Sahih al-Bukhari 4477
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · The Statement of Allah "...Then do not set up rivals unto Allah (in worship) while you know (that He Alone has the right to be worshipped)..." (V.2:22)
Narrated `Abdullah:
حَدَّثَنِي عُثْمَانُ بْنُ أَبِي شَيْبَةَ ، حَدَّثَنَا جَرِيرٌ ، عَنْ مَنْصُورٍ ، عَنْ أَبِي وَائِلٍ ، عَنْ عَمْرِو بْنِ شُرَحْبِيلَ ، عَنْ عَبْدِ اللَّهِ ، قَالَ سَأَلْتُ النَّبِيَّ صلى الله عليه وسلم أَىُّ الذَّنْبِ أَعْظَمُ عِنْدَ اللَّهِ قَالَ " أَنْ تَجْعَلَ لِلَّهِ نِدًّا وَهْوَ خَلَقَكَ ". قُلْتُ إِنَّ ذَلِكَ لَعَظِيمٌ، قُلْتُ ثُمَّ أَىُّ قَالَ " وَأَنْ تَقْتُلَ وَلَدَكَ تَخَافُ أَنْ يَطْعَمَ مَعَكَ ". قُلْتُ ثُمَّ أَىُّ قَالَ " أَنْ تُزَانِيَ حَلِيلَةَ جَارِكَ " .
I asked the Prophet, "What is the greatest sin in the Sight of Allah?" He said, "That you set up a rival unto Allah though He Alone created you." I said, "That is indeed a great sin." Then asked, "What is next?" He said, "To kill your son lest he should share your food with you." I asked, "What is next?" He said, "To commit illegal sexual intercourse with the wife of your neighbor."