Hadith 4
The Book of Fighting [The Prohibition of Bloodshed]
It was narrated that 'Abdullah said:
"I asked the Messenger of Allah [ﷺ], which sin is most grievous?" He said: "Shirk, setting up a rival to Allah, committing adultery with your neighbor's wife, and killing your child for fear of poverty, and that he may eat with you." Then 'Abdullah recited the Verse: "And those who invoke not any other Ilah (god) along with Allah."
أَخْبَرَنَا عَبْدَةُ، قَالَ أَنْبَأَنَا يَزِيدُ، قَالَ أَنْبَأَنَا شُعْبَةُ، عَنْ عَاصِمٍ، عَنْ أَبِي وَائِلٍ، عَنْ عَبْدِ اللَّهِ، قَالَ سَأَلْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم أَىُّ الذَّنْبِ أَعْظَمُ قَالَ
الشِّرْكُ أَنْ تَجْعَلَ لِلَّهِ نِدًّا وَأَنْ تُزَانِيَ بِحَلِيلَةِ جَارِكَ وَأَنْ تَقْتُلَ وَلَدَكَ مَخَافَةَ الْفَقْرِ أَنْ يَأْكُلَ مَعَكَ
Hadith gradings, numbering and translations can differ between editions. For legal rulings or detailed interpretation, consult qualified scholarship and the referenced edition.