Surah 2. Al-Baqara, Ayah 194

This is a free rendering of the phrase "the sacred month for the sacred month", which is interpreted by all commentators in the sense given above. The "sacred months" during which, according to ancient Arab custom, all fighting was deemed utterly wrong, were the first, seventh, eleventh and twelfth months of the lunar calendar.

Thus, although the believers are enjoined to fight back whenever they are attacked, the concluding words of the above verse make it clear that they must, when fighting, abstain from all atrocities, including the killing of non-combatants.

 The sacred months are the 1 st , 7 th , 11 th , and 12 th  months of the Islamic calendar.

Haram - prohibited, sacred. The month of Pilgrimage (Zul-hajj) was a sacred month, in which warfare was prohibited by Arab custom. The month preceding (Zul-qad) and the month following (Muharram) were included in the prohibition, and Muharram was specially called al-Haram. Possibly Muharram is meant in the first line, and the other months and other prohibited things in "all things prohibited". In Rajab, also, war was prohibited. If the pagan enemies of Islam broke that custom and made war in the prohibited months, the Muslims were free also to break that custom but only to the same extent as the other broke it. Similarly the territory of Mecca was sacred, in which war was prohibited. If the enemies of Islam broke that custom, the Muslims were free to do so to that extent. Any convention is useless if one party does not respect it. There must be a law of equality. Or perhaps the word reciprocity may express it better.

At the same time the Muslims are commanded to exercise self-restraint as much as possible. Force is a dangerous weapon. It may have to be used for self-defence or self-preservation, but we must always remember that self-restraint is pleasing in the eyes of God. Even when we are fighting, it should be for a principle, not out of passion.