Allah does not forgive the sin of association with Him 4:50
4:48 Allah does not forgive (the sin of inventing an) association with Him, but He forgives other (sins) to whomsoever He will. He who associates with Allah has invented a great sin.
4:49 Have you not seen those who exalt themselves? Rather, Allah purifies whom He will and they shall not be wronged a single tissue that covers a date stone.