The polytheists fought them in the year of Hudaybiyyah in the sacred month, which is Dhul-Qi'dah. It was said to them upon their departure for the Umrah of Qada, and their dislike of fighting, that in Dhul-Qi'dah: 'The sacred month is by the sacred month,' meaning this month is like that month, and its sanctity is violated by its violation. This means you violate its sanctity upon them as they violated its sanctity upon you. And the sacred matters are retribution, meaning every sanctity in which retribution is applied for the violation of any sanctity, is to be avenged by violating its sanctity. So when they violated the sanctity of your month, do likewise to them and do not worry. This is emphasized by His saying: 'So whoever transgresses against you, transgress against him in a manner similar to that in which he has transgressed against you, and fear Allah while you are being victorious over those who have transgressed against you, and do not transgress to what is not permissible for you.'