Quran 4:48-50

48 God forgives not that aught should be with Him associated; less than that He forgives to whomsoever He will. Whoso associates with God anything, has indeed forged a mighty sin. 49 Hast thou not regarded those who purify themselves? Nay; only God purifies whom He will; and they shall not be wronged a single date-thread. 50 Consider how they forge falsehood against God; and that suffices for a manifest sin;