At-Tawbah 9:36

Inna AAiddata ashshuhoori AAinda Allahiithna AAashara shahran fee kitabi Allahiyawma khalaqa assamawati wal-ardaminha arbaAAatun hurumun thalika addeenualqayyimu fala tathlimoo feehinna anfusakumwaqatiloo almushrikeena kaffatan kama yuqatiloonakumkaffatan waAAlamoo anna Allaha maAAaalmuttaqeen

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. That is the correct religion [i.e., way], so do not wrong yourselves during them. And fight against the disbelievers collectively as they fight against you collectively. And know that Allāh is with the righteous [who fear Him].

Surely, the number of months according to Allah is twelve (as written) in the Book of Allah on the day He created the heavens and the Earth, of which there are Four Sacred Months. That is the right faith. So, do not wrong yourself therein. And fight the Mushriks all together, as they fight you all together, and be sure that Allah is with the God-fearing.