Quran 2:217

يَسۡـَٔلُونَكَ عَنِ ٱلشَّہۡرِ ٱلۡحَرَامِ قِتَالٍ۬ فِيهِ‌ۖ قُلۡ قِتَالٌ۬ فِيهِ كَبِيرٌ۬‌ۖ وَصَدٌّ عَن سَبِيلِ ٱللهِ وَڪُفۡرُۢ بِهِۦ وَٱلۡمَسۡجِدِ ٱلۡحَرَامِ وَإِخۡرَاجُ أَهۡلِهِۦ مِنۡهُ أَكۡبَرُ عِندَ ٱللهِ‌ۚ وَٱلۡفِتۡنَةُ أَڪۡبَرُ مِنَ ٱلۡقَتۡلِ‌ۗ وَلَا يَزَالُونَ يُقَـٰتِلُونَكُمۡ حَتَّىٰ يَرُدُّوكُمۡ عَن دِينِڪُمۡ إِنِ ٱسۡتَطَـٰعُواْ‌ۚ وَمَن يَرۡتَدِدۡ مِنكُمۡ عَن دِينِهِۦ فَيَمُتۡ وَهُوَ ڪَافِرٌ۬ فَأُوْلَـٰٓٮِٕكَ حَبِطَتۡ أَعۡمَـٰلُهُمۡ فِى ٱلدُّنۡيَا وَٱلۡأَخِرَةِ‌ۖ وَأُوْلَـٰٓٮِٕكَ أَصۡحَـٰبُ ٱلنَّارِ‌ۖ هُمۡ فِيهَا خَـٰلِدُونَ ٢١٧

They ask you about the Sacred Months and fighting therein: say, "Fighting therein is a sacrilege. However, repelling from the path of ALLAH and disbelieving in Him and in the sanctity of the Sacred Masjid, and evicting its people, are greater sacrileges in the sight of ALLAH. Oppression is worse than murder." They will always fight you to revert you from your religion, if they can. Those among you who revert from their religion, and die as disbelievers, have nullified their works in this life and the Hereafter. These are the dwellers of Hell, wherein they abide forever.