At-Tawbah 9:36

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 36

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