Quran 4, An-Nisa (the Women) ⓘ

4:48Lo! Allah forgiveth not that a partner should be ascribed unto Him. He forgiveth (all) save that to whom He will. Whoso ascribeth partners to Allah, he hath indeed invented a tremendous sin.

إِنَّ اللَّهَ لَا يَغْفِرُ أَنْ يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَلِكَ لِمَنْ يَشَاءُ وَمَنْ يُشْرِكْ بِاللَّهِ فَقَدِ افْتَرَى إِثْمًا عَظِيمًا