Ali ibn Ibrahim (may Allah have mercy on him): Some of the times are known and well-known, and others are unspecified. The known and well-known times are four, which are: the sacred months that Allah mentioned in the verse: مِنْهَا أَرْبَعَةٌ حُرُمٌ [of which four are sacred]. There are twelve months which Allah created and which are identified by the crescent moon; the first of them is Muharram and the last of them is Dhul-Hijjah. The sacred months are four, which are: Rajab alone, and also Dhul-Qa'dah, Dhul-Hijjah and Muharram consecutively, in which Allah forbade fighting, and in which sins and good deeds are multiplied. The months of siyahah (safe travel) are known, which are: twenty days of Dhul-Hijjah, Muharram, Safar, Rabi' al-Awwal and ten days of Rabi' al-Thani, in which Allah delayed fighting the polytheists by sending down the verse فَسِیحُوا فِی الْأَرْضِ أَرْبَعَةَ أَشْهُرٍ [travel through the earth for four months]. The months of Hajj are known, which are: Shawwal, Dhul-Qa'dah and Dhul-Hijjah. These months are called "the months of Hajj" because whoever goes to perform umrah in these months — that is, in Shawwal or Dhul-Qa'dah or Dhul-Hijjah — and intends to remain in Makkah so as to also perform the Hajj, may after the umrah perform Hajj al-Tamattu' as well. But whoever goes for umrah in months other than these, whether he intends to remain in Makkah for Hajj or does not intend so, cannot perform Hajj al-Tamattu', because he did not enter Makkah in the months of Hajj [and for tamattu' he must exit Makkah and re-enter]. So this is the reason these months are named the months of Hajj. Allah, Blessed and Exalted, says: الْحَجُّ أَشْهُرٌ مَعْلُومَاتٌ [Hajj is (during) well-known months]. Likewise, the month of Ramadan is among the known times. As for the unspecified times, they are months in which, when a matter befalls [the Muslims], one must wait until they come to an end. They are: the waiting period ('iddah) of divorced women and of women whose husbands have died. So whenever a husband divorces his wife, if that woman is not past menopause and menstruates, she must — for the number of times that Allah the Exalted has specified — become pure from menstrual blood; and if that woman is past menopause and does not menstruate, she must observe an 'iddah of three months in which she sees no blood. Likewise, the 'iddah of a woman whose husband has died is four months and ten days, and the 'iddah of a divorced woman who is pregnant is until she delivers. Likewise, the 'iddah of a woman who has become forbidden to her husband on account of ila' (the man's oath not to have relations with his wife in order to hurt her) is four months. Among the other cases of unspecified times is the term fixed in a loan between the lender and the borrower. Also among them are the two consecutive months of fasting obligatory in the expiation of zihar (a man's declaring his wife forbidden to himself) and in the expiation of unintentional killing. Another of them is the fasting obligatory in Hajj upon one who cannot find the sacrificial animal. [The last case is] the three days of fasting obligatory in the expiation of an oath. Thus these are the known times and the unspecified times which Allah mentioned in the verse: يَسْأَلُونَكَ عَنِ الْأَهِلَّةِ قُلْ هِيَ مَوَاقِيتُ لِلنَّاسِ وَالْحَجِّ [They ask you concerning the new moons. Say: They are appointed times for the people and for the Hajj].