Although the above chapter dealt with the types of fast, we decided to expand this discussion and quote for you from "Bab al-Sawm," chapter dealing with fast, on pp. 52-54, Vol. 2, of Man la Yahduruhu al-Faqih by the nation's mentor Shaikh Abu Ja’far Muhammad ibn Ali ibn al-Husayn ibn Babawayh al-Qummi al-Saduq who indicates the following:
Al-Zuhri (one of the companions of our fourth Imam Ali ibn al-Husayn ibn Ali ibn Abu Talib Zaynul-’Abidin al-Sajjad, peace be upon him and his posterity as well as progeny) is quoted saying, "Ali ibn al-Husayn, peace be upon them, asked me once, ‘Where did you come from, O Zuhri?' I said, ‘From the [Prophet's] mosque.' ‘What were you discussing?' he asked me. ‘We discussed the fast,' said I, ‘and we all agreed that the only obligatory fast is the fast of the month of Ramadhan.'
He said to me, ‘O Zuhri! It is not as you all say. Fast is of forty different types: ten are as obligatory as the fast of the month of Ramadhan; ten are prohibited; fourteen are optional: one may fast during them or he may not; add to that the three different kinds of conditional fast. Add also: disciplinary fast, permissible fast, and the fast making up for one who had to go on a journey or who fell sick.' Said I, ‘May I be sacrificed for your sake! Please explain them to me.'"
The Imam (as) stated the following:
"Obligatory fast includes the fast of the month of Ramadhan and of two consecutive months for each one day deliberately missed of the month of Ramadhan, and the fast of two consecutive months as an atonement for zihar. Allah, the most Sublime, the most Exalted, says,
‘(As for) those of you who put away their wives by likening their backs to the backs of their mothers, these are not their mothers; their mothers are no other than those who gave birth to them, and most surely they utter a hateful word and a falsehood, and most surely Allah is Pardoning, Forgiving. (As for) those who put away their wives by likening their backs to the backs of their mothers then recall what they said, they should free a captive before touching each other; to that you are admonished (to conform), and Allah is Aware of what you do. But whoever has no (such) means, let him fast for two months succesively before they touch each other' (Holy Qur'an, Surah Mujadilla 58-2-4).
Another (such type of obligatory fast) is fasting two successive months if a Muslim kills another Muslim by mistake and is unable to free a slave; this is obligatory on account of the verse saying:
‘And whoever kills a believer by mistake should free a believing slave, and blood-money should be paid to his people unless they remit it as alms; but if they be from a tribe hostile to you and he is a believer, the freeing of a believing slave (suffices), and if he is from a tribe between whom and you there is a covenant, the blood-money should be paid to his people along with the freeing of a believing slave; but if he cannot find (a slave), he should fast for two months successively: a penance from Allah, and Allah is Knowing, Wise' (Holy Qur'an, Surah Nisa 4:92).
Another (such obligatory fast) is fasting three days as an act of atonement for breaking an oath if one is unale to feed the needy; Allah, the most Sublime, the most High, says,
‘Allah does not call you to account for what is vain of your oaths, but He calls you to account for making deliberate oaths; so, its expiation is the feeding of ten poor men out of the middling (food) whereby you feed your families, or their clothing, or the freeing of a slave; but whosoever cannot find (means), he, then, should fast for three days; this is the expiation of your oaths when you swear' (Holy Qur'an, Surah Maida 5:89).
All types of such fast are consecutive, not a day now and a day then.
"And the fast on account of causing an injury to the head while shaving it while performing the pilgrimage rites is also obligatory; Allah Almighty says, ‘Whoever among you is sick or has an ailment of the head, he (should effect) a compensation by fasting or offering alms or sacrificing' (Holy Qur'an, Surah Baqarah 2:196).
So he is given in this verse an option: if he chooses to fast, he should fast for three days. And the fast of one who cannot offer a sacrifice at the pilgrimage is also obligatory; Allah Almighty says,
‘Whoever benefits by combining the visit with the pilgrimage (should take) what offering is easy (for him) to obtain; but he who cannot find (any offering) should fast for three days during the pilgrimage and for seen days when you return; these (make) ten (days) complete' (Holy Qur'an, Surah Baqarah 2:196).
And the fast of one who hunts while still wearing the ihram is also obligatory; Allah, the most Exalted, the most Sublime, says,
‘O you who believe! Do not kill game while you are on pilgrimage, and whoever among you kills it intentionally, the compensation (for it) is the like of what he kills, from the cattle, as two just persons among you shall judge, as an offering to be brought to the Ka’ba or the expiation (of it) is the feeding of the poor or the equivalent of it in fasting so that he may taste the unwholesome result of his deed' (Holy Qur'an, Surah Maida 5:95)."
Then the Imam (as) turned to al-Zuhri and asked him, "Do you know how its equivalent is met by fasting, O Zuhri?" The latter said, "No, indeed, I do not know." Imam Zaynul-’Abidin (as) then said, "The game is first to be estimated, then the estimated value is to be measured by its equivalent in charity, then such a measure is to be weighed, so he should fast one day for each half a measure unit.
And the covenant (nathr) fast is obligatory, and so is the fast of I’tikaf. As regarding the prohibited fast, it is forbidden to fast on Eid al-Fitr, Eid al-Adha, the three days of tashreeq1, and the fast of doubt: Allah ordered us to fast it with the month of Sha’ban and anyone among us is prohibited from singling himself out to fast when everyone else is not sure whether it is the inception of the month of Ramadhan or not."
I said to him, "May I be sacrificed for you, but if he did not fast during the month of Sha’ban, what should he do?" The Imam (as) said, "He should make the intention on the uncertain night that he is fasting the month of Sha’ban; so, if it turns out to be the month of Ramadhan, he will receive his reward, but if it becomes evident that it was, indeed, the month of Sha’ban, he will not have committed any harm."
I then asked him, "How can voluntary fast make up for a compulsory one?" He (as) said, "If someone voluntarily fasts one day during the month of Ramadhan without knowing that it is the month of Ramadhan, then he finds out that it was, should he fast again?! The obligation is regarding the day itself. The wisal fast2 is prohibitive, and to fast each day of your life is likewise prohibitive.
"As regarding optional fast, it is to fast on Fridays, Thursdays, and Mondays, the white (beed) days 3, the fast of six days during the month of Shawwal following the month of Ramadhan, the fast on the standing day at Arafat, and the day of Ashura; all these occasions are optional; one may or may not fast during them.
As regarding the fast by permission, a woman cannot fast an optional fast without the permission of her husband; a slave may not observe an optional fast without the permission of his master; and a guest may not fast an optional fast except with the permission of his host; the Messenger of Allah (S) has said, ‘Whoever visits some folks, he should not observe an optional fast except with their permission.'
As regarding disciplinary fast, a boy reaching adolescence is ordered to fast when he reaches the age of adulthood, though it is not obligatory on him to do so. Likewise, if one is forced due to a sudden ailment to break his fast at the inception of the day, then he gains his strength thereafter, he should fast the rest of the day as a self-disciplinary act although he is not obligated to do so.
Likewise, if a traveller eats at the beginning of the day then reaches home, he should abstain from eating the rest of the day as a self-disciplinary act and not as an obligation. As regarding the fast of one who forgets and eats or drinks, or if he does so only as a measure of taqiyya4, without doing so on purpose, Allah, the most Exalted, the most Great, has permitted him to do so and will reward him for it. As regarding the fast when travelling or suffering from an ailment, there is a great deal of difference of opinion in its regard. Some people say that he should fast, whereas others say that he should not.
As far as we (Ahl al-Bayt [as]) are concerned, we are of the view that one should break his fast during both cases; so, if he fasts during his trip, or when sick, he has to make it up because Allah, the most Exalted, the most Great, says, "And if one of you is sick or travelling, (the fast of) a number of other days (suffices)'."