Surat At-Tawbah (36-37)

{إِنَّ عِدَّةَ الشُّهُورِ عِندَ اللّهِ اثْنَا عَشَرَ شَهْراً فِي كِتَابِ اللّهِ يَوْمَ خَلَقَ السَّمَاوَات وَالأَرْضَ مِنْهَا أَرْبَعَةٌ حُرُمٌ ذَلِكَ الدِّينُ الْقَيِّمُ فَلاَ تَظْلِمُواْ فِيهِنَّ أَنفُسَكُمْ وَقَاتِلُواْ الْمُشْرِكِينَ كَآفَّةً كَمَا يُقَاتِلُونَكُمْ كَآفَّةً وَاعْلَمُواْ أَنَّ اللّهَ مَعَ الْمُتَّقِينَ} [التوبة:  36]

36- The number of months as ordained by Allah who commanded His Servants to abide by is twelve [in the form of the well-known lunar months] as recorded in the Preserved Tablet, of which there are four sacred months: Muharram, Rajab, Dhul-Qa`dah, and Dhul-Hijjah. This is the straight Shari`ah that cannot be changed or altered, so do not oppress yourselves by exposing it to the punishment of Allah if you commit forbidden actions during these months; these inviolable months should be peaceful and secure.

Fight all polytheists because they fight all Muslims without excluding any of them. It is a battle between faith and polytheism, the truth and falsehood. O Muslims, let it be known that Allah supports His Believing Servants by providing them victory, so fear Allah to win His Guardianship.

The most famous view is that the inviolability of fighting during these month was abrogated according to Allah's Saying: "Then kill the Mushrikûn wherever you find them" [Surat At-Tawbah: 5].

However, the inviolability of these Sacred months remains because they are connected with the time of Hajj and because committing sins during these months requires double and severe punishment. Muslims should not add or omit to the number of these months as was mentioned in the following Ayah.

{إِنَّمَا النَّسِيءُ زِيَادَةٌ فِي الْكُفْرِ يُضَلُّ بِهِ الَّذِينَ كَفَرُواْ يُحِلِّونَهُ عَاماً وَيُحَرِّمُونَهُ عَاماً لِّيُوَاطِؤُواْ عِدَّةَ مَا حَرَّمَ اللّهُ فَيُحِلُّواْ مَا حَرَّمَ اللّهُ زُيِّنَ لَهُمْ سُوءُ أَعْمَالِهِمْ وَاللّهُ لاَ يَهْدِي الْقَوْمَ الْكَافِرِينَ} [التوبة: 37]

37- Increasing the number of months or the number of days as Arabs in the Pre-Islamic Period used to do to make war violable is just an increase in their disbelief because it makes what Allah has forbidden lawful. It also contains violation to the Shari`ah and distortion to the creed by which polytheists are going astray because of that manipulation and distortion. They made the last inviolable month lawful by replacing it with another month to push away the sin of what they had done during that month. They thought they did something good and turned deviation into straightness and error into guidance, but Allah does not guide whoever keeps away from the signs of guidance and insists on disbelief.

Some of the People in the Pre-Islamic Period used to call Al Muharram as Safar to make fighting lawful and prohibit fighting in Safar and call it Al Muharram, whereas others used to forbidden the month one year and lawfulize it another year.