Surah At-Tawbah, ayah 36

إِنَّ عِدَّةَ ٱلشُّهُورِ عِندَ ٱللَّهِ ٱثۡنَا عَشَرَ شَهۡرٗا فِي كِتَٰبِ ٱللَّهِ يَوۡمَ خَلَقَ ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضَ مِنۡهَآ أَرۡبَعَةٌ حُرُمٞۚ ذَٰلِكَ ٱلدِّينُ ٱلۡقَيِّمُۚ فَلَا تَظۡلِمُواْ فِيهِنَّ أَنفُسَكُمۡۚ وَقَٰتِلُواْ ٱلۡمُشۡرِكِينَ كَآفَّةٗ كَمَا يُقَٰتِلُونَكُمۡ كَآفَّةٗۚ وَٱعۡلَمُوٓاْ أَنَّ ٱللَّهَ مَعَ ٱلۡمُتَّقِينَ ٣٦

Inna 'iddatash-shuhūri 'indallāhithnā 'ashara shahran fī kitābillāhi yawma khalaqas-samāwāti wal-arda minhā arba'atun hurumun dhālikad-dīnul-qayyimu falā tazlimū fīhinna anfusakum waqātilul-mushrikīna kāffatan kamā yuqātilūnakum kāffatan wa'lamū annallāha ma'al-muttaqīn

Indeed, the number of months with Allāh is twelve [lunar] months in the register of Allāh [from] the day He created the heavens and the earth; of these, four are sacred.⁴⁷¹ That is the correct religion [i.e., way], so do not wrong yourselves during them.⁴⁷² And fight against the disbelievers collectively as they fight against you collectively. And know that Allāh is with the righteous [who fear Him].