Shirk (Polytheism/Association of Partners with Allah)

وَإِذْ قَالَ لُقْمَـٰنُ لِٱبْنِهِۦ وَهُوَ يَعِظُهُۥ يَـٰبُنَىَّ لَا تُشْرِكْ بِٱللَّهِ ۖ إِنَّ ٱلشِّرْكَ لَظُلْمٌ عَظِيمٌ

And [mention, O Muḥammad], when Luqmān said to his son while he was instructing him, "O my son, do not associate [anything] with Allāh. Indeed, association [with Him] is great injustice."

إِنِّىٓ إِذًا لَّفِى ضَلَـٰلٍ مُّبِينٍ

Indeed, I would then be in manifest error.

وَلَقَدْ أُوحِىَ إِلَيْكَ وَإِلَى ٱلَّذِينَ مِن قَبْلِكَ لَئِنْ أَشْرَكْتَ لَيَحْبَطَنَّ عَمَلُكَ وَلَتَكُونَنَّ مِنَ ٱلْخَـٰسِرِينَ

And it was already revealed to you and to those before you that if you should associate [anything] with Allāh, your work would surely become worthless, and you would surely be among the losers.