(The Unforgivable Sin)
God does not forgive idolatry,* but He forgives lesser offenses for whomever He wills. Anyone who sets up idols beside God, has forged a horrendous offense.
إِنَّ اللَّهَ لا يَغفِرُ أَن يُشرَكَ بِهِ وَيَغفِرُ ما دونَ ذٰلِكَ لِمَن يَشاءُ وَمَن يُشرِك بِاللَّهِ فَقَدِ افتَرىٰ إِثمًا عَظيمًا
innal laaha laa yaghfiru ai yushraka bihee wa yaghfiru maa doona zaalika limai yashaaa’; wa mai yushrik billaahi faqadif taraaa isman ‘azeemaa
*4:48 Idol worship is not forgivable, if maintained until death. One can always repent from any offense, including idolatry, before death comes (see 4:18 & 40:66).