Surah 9. Al-Tawba, Ayah 37

Lit., "is but an increase in denying the truth (kufr)". The term nasi', rendered by me as "intercalation", may also be translated as "postponement" - i.e., the postponement of lunar months by means of the periodical intercalation of a thirteenth month, as practiced by the pre-Islamic Arabs with a view to bringing the traditional lunar calendar, for purely worldly reasons, into accord with the solar year (see note [54] above). The Qur'an describes this practice as an additional instance of kufr because it contravenes God's declared will as regards the observance of the lunar calendar in respect of various religious duties (cf. the preceding verse, as well as 2:189 and the corresponding note [165]).

An allusion to the arbitrary manner in which the pre-Islamic Arabs intercalated a thirteenth month in the third, sixth and eighth year of every eight-year period.

By means of the intercalation spoken of above, the pagan Arabs did in most years keep the number of months to twelve; but by divorcing the four "sacred months" (Muharram, Rajab, Dhu 'l-Qa'dah and Dhu 'l-Hijjah), from their proper lunar context they obviously profaned and perverted the natural law.

 The sacred months are the 11 th , 12 th , 1 st , and 7 th  of the Islamic calendar. Since the polytheists knew that it was forbidden to fight in the sacred months, they used to transfer the sanctity to other months, say for example, the 3 rd , 4 th , 8 th , and 10 th  as long as they maintained the sanctity of any four months throughout the year.

Cf. vi. 122. The lawless man thinks he is doing a great thing in getting the better of those who are careful to observe a law they believe in. But the lawless man loses the guidance of Faith he will therefore lose in the end.

To meddle with an old-established custom of close time for warfare during Prohibited or Sacred Months was not only a demonstration of the Unbelievers against the Muslims on account of their Faith, but was wrong and unjust in itself, as it abolished a wholesome check on unregulated warfare, and prejudiced the law-abiding side by arbitrary decisions.