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.1 That is the correct religion [i.e., way], so do not wrong yourselves during them.2 And fight against the disbelievers collectively as they fight against you collectively. And know that Allāh is with the righteous [who fear Him].
Translation: Saheeh International (English)
1 See footnote to 9:5.
2 i.e., do not violate the sacred months or commit aggression therein.
There are twelve months of the year decreed by Allah, no more or less, which Allah established in the Preserved Tablet when He created the heavens and the earth. Of these twelve months, four are sacred, during which Allah has forbidden fighting. Three of them consecutive (Dhū Al-Qa‘dah, Dhū Al-Ḥijjah and Muḥarram), and one is on its own (Rajab). The twelve months of the year, and respecting the sacredness of four of them, is the correct way of life. Allah tells the believers not to wrong themselves during these sacred months by fighting, violating their sacredness. Also, the believers are instructed to fight the idolaters all together as they fight them all together, and to know that Allah is with those who are Mindful, who follow what He instructs and stay away from what He has prohibited, and He helps and supports them. If Allah supports anyone, no one will be able to defeat them.