Quran 9:84

وَلَا تُصَلِّ عَلَىٰٓ أَحَدٍ۬ مِّنۡہُم مَّاتَ أَبَدً۬ا وَلَا تَقُمۡ عَلَىٰ قَبۡرِهِۦۤ‌ۖ إِنَّہُمۡ كَفَرُواْ بِٱللهِ وَرَسُولِهِۦ وَمَاتُواْ وَهُمۡ فَـٰسِقُونَ ٨٤

You shall not observe the funeral prayer for any of them when he dies, nor shall you stand at his grave. They have disbelieved in ALLAH and His messenger, and died in a state of wickedness.