Surah At-Taubah (The Repentance), Verse 36

اِنَّ عِدَّةَ الشُّهُوْرِ عِنْدَ اللّٰهِ اثْنَا عَشَرَ شَهْرًا فِیْ كِتٰبِ اللّٰهِ یَوْمَ خَلَقَ السَّمٰوٰتِ وَالْاَرْضَ مِنْهَاۤ اَرْبَعَةٌ حُرُمٌ ذٰلِكَ الدِّیْنُ الْقَیِّمُ فَلَا تَظْلِمُوْا فِیْهِنَّ اَنْفُسَكُمْ وَقَاتِلُوا الْمُشْرِكِیْنَ كَآفَّةً كَمَا یُقَاتِلُوْنَكُمْ كَآفَّةً وَاعْلَمُوْۤا اَنَّ اللّٰهَ مَعَ الْمُتَّقِیْنَ ۟

Inna 'iddatash shuhoori 'indal laahis naa 'ashara shahran fee Kitaabil laahi yawma khalaqas samaawaati wal arda minhaaa arba'atun hurum; zaalikad deenul qaiyim; falaa tazlimoo feehinna anfusakum; wa qaatilul mushrikeena kaaaffatan kamaa yuqaati loonakum kaaaffah; wa'lamooo annal laaha ma'al muttaqeen

“The number of months in the sight of Allah is twelve (in a year)- so ordained by Him the day He created the heavens and the earth; of them four are sacred: that is the straight usage. So wrong not yourselves therein, and fight the Pagans all together as they fight you all together. But know that Allah is with those who restrain themselves.”

Quran 9:36 (Yusuf Ali Translation)