As a precaution, it is said that it is recommended to fast on the Day of Doubt [Yowm al-Shakk]. This day is the day that one is unsure if it is the last day of Sha`baan or the first day of Ramadhan, due to the crescent not being sighted. However, many fast this day with the wrong intention, which is considered forbidden, and in some cases they would be required to repeat the fast. The following is an analysis and clarification.

For summary of the ruling, please see the last two rulings (fatwas) by Sayed al-Sistani (hf).

There are many hadiths which confirm one can, or should, perform this fast:

محمد بن يعقوب، عن عدة من أصحابنا، عن أحمد بن محمد، عن حمزة بن يعلى، عن زكريا بن آدم، عن الكاهلي قال: سألت أبا عبد الله عليه السلام عن اليوم الذي يشك فيه من شعبان، قال: لان أصوم يوما من شعبان أحب إلي من أن أفطر يوما من شهر رمضان
[the narrator asked] Aba Abdillah [al-Sadiq] (as) about the fasting on the day in which he doubts if it is Sha`baan [or Ramadhan]. He (as) replied: “Because fasting a day from Sha`baan is more beloved to me than not fasting (- or breaking the fast on) a day from the Month of Ramadhan.

Source: al-Kafi, Volume 4, Page 82, Hadith #1; al-Tahdheeb, Volume 4, Page 181, Hadith #505, al-Istibsar, Volume 2, Page 78, Hadith #237; Wasaa’il al-Shia, Volume 10, Page 20, Hadith #1 / 12730 (See Reference One below)

Grading: al-Majlisi says it is Hasan/Good (حسن) [Mir’aat al-Uqool, Volume 16, Page 238] (See Reference Two below)

وعن علي بن إبراهيم ، عن أبيه ، عن ابن أبي عمير ، عن معاوية بن وهب قال : قلت لابي عبدالله ( عليه السلام ) : الرجل يصوم اليوم الذي يشك فيه من شهر رمضان فيكون كذلك ؟ فقال : هو شيء وفق له
It was said to Abi Abdillah [al-Sadiq] (as):  “A man fasts the day in which he doubts if [the day] is of [the first of] the Month of Ramadhan, and it turns out that it is?” He [al-Sadiq] replied: “It is something in which he has succeeded.”

Source: al-Kafi, Volume 4, Page 82, Hadith #3; Wasaa’il al-Shia, Volume 10, Page 22, Hadith #5 / 12734 (See Reference One below)

Grading: Sayed Sadiq al-Rohani says it is Authentic/Sahih (صحيح) [Fiqh al-Sadiq, Volume 12, Page 44]; al-Majlisi says it is Hasan/Good (حسن) [Mir’aat al-Uqool, Volume 16, Page 239] (See Reference Two below)

وبالاسناد عن محمد بن أبي الصهبان، عن محمد بن بكر بن جناح، عن علي ابن شجرة، عن بشير النبال، عن أبي عبد الله عليه السلام قال: سألته عن صوم يوم الشك فقال: صمه، فإن يك من شعبان كان تطوعا، وإن يك من شهر رمضان فيوم وفقت له
Abi Abdillah [al-Sadiq] (as) was asked about the fasting on the day of doubt, so he (as) replied: “Fast it, for if it turns out it is from Sha`baan, it is considered a voluntary [fast], and if it turns out to be from the Month of Ramadhan, then it is a day in which he has succeeded.”

Source: al-Kafi, Volume 4, Page 82, Hadith #5; al-Tahdheeb, Volume 4, Page 181, Hadith #504, al-Istibsar, Volume 2, Page 78, Hadith #236; Wasaa’il al-Shia, Volume 10, Page 21, Hadith #3 / 12732 (See Reference One below)

Grading: al-Majlisi says it is Hasan/Good (حسن) [Mir’aat al-Uqool, Volume 16, Page 239] (See Reference Two below)

Now that it is established that it is recommended, there needs to be a discussion about intention, which is stressed upon in the following hadiths:

وعن محمد بن يحيى، عن أحمد بن محمد، عن عثمان بن عيسى، عن سماعة قال: قلت لأبي عبد الله عليه السلام: رجل صام يوما ولا يدري أمن شهر رمضان هو أو من غيره فجاء، قوم فشهدوا أنه كان من شهر رمضان، فقال بعض الناس عندنا لا يعتد به فقال: بلى فقلت: إنهم قالوا: صمت وأنت لا تدري أمن شهر رمضان هذا أم من غيره؟ فقال: بلى فاعتد به فإنما هو شئ وفقك الله له، إنما يصام يوم الشك من شعبان، ولا يصومه من شهر رمضان لأنه قد نهي أن ينفرد الانسان بالصيام في يوم الشك، وإنما ينوي من الليلة أنه يصوم من شعبان، فإن كان من شهر رمضان أجزأ عنه بتفضل الله وبما قد وسع على عباده، ولولا ذلك لهلك الناس.
[The narrator] said to Abi Abdillah [al-Sadiq] (as): “A man fasts a day and he does not know whether it is from the Month of Ramadhan, or from other than it [i.e. the Month of Sha’baan], so there came to him a people testifying in that it is from [the Month of] Ramadhan. Some of our people said ‘we do not consider it [to be from the Month of Ramadhan]'”. He (as) replied: “Yes? [go on]”. I the narrator] continued: “They [some of our people] said: ‘You fasted while you do not know if it [the day] is from [the Month of] Ramadhan or other than it?'”. He [al-Sadiq] (as) said: “Yes, and count it, for indeed it is something Allah has given you success through. Verily, one should fast the day of doubt [with the intention] it is of Sha`baan, and do not fast it [with the intention] it is from the Month of Ramadhan, because it has been forbidden for one to fast alone on the day of doubt, while indeed, one should have the intention from the [previous] night that he fasts it from Sha`baan. If it turns out it is from the month of Ramadhan, it is suffices for him by the Grace of Allah (azwj) and by what he has distributed upon his servants, for if it were not for this, mankind would have been destroyed.”

Source: al-Kafi, Volume 4, Page 82, Hadith #6; al-Tahdheeb, Volume 4, Page 182, Hadith #508, al-Istibsar, Volume 2, Page 79, Hadith #240; Wasaa’il al-Shia, Volume 10, Page 21, Hadith #4 / 12733 (See Reference One below)

Grading: Sayed Sadiq al-Rohani says it is Reliable/Muwathaq (موثق) [Fiqh al-Sadiq, Volume 12, Page 45]; al-Majlisi says it is Reliable/Muwathaq (موثق) [Mir’aat al-Uqool, Volume 16, Page 239] (See Reference Two below)

وعن علي بن إبراهيم، عن أبيه، عن القاسم بن محمد الجوهري، عن سليمان ابن داود، عن سفيان بن عيينة، عن الزهري، عن علي بن الحسين عليه السلام – في حديث طويل – قال وصوم يوم الشك أمرنا به ونهينا عنه، أمرنا به أن نصومه مع صيام شعبان، ونهينا عنه أن ينفرد الرجل بصيامه في اليوم الذي يشك فيه الناس، فقلت له: جعلت فداك فإن لم يكن صام من شعبان شيئا كيف يصنع؟ قال: ينوي ليلة الشك أنه صائم من شعبان، فإن كان من شهر رمضان أجزأ عنه، وإن كان من شعبان لم يضره، فقلت: وكيف يجزي صوم تطوع عن فريضة؟ فقال: لو أن رجلا صام يوما من شهر رمضان تطوعا وهو لا يعلم أنه من شهر رمضان ثم علم بذلك لأجزأ عنه، لان الفرض إنما وقع على اليوم بعينه
 Ali ibn al-Hussain [al-Sajjad] (as) – in a long hadith – said: “[In regards] to fasting the day of doubt, we have [both] ordered it, and forbid it. We have ordered it in that fasting it as a part of the fasts of Sha`baan, and we have forbid it in one fasting alone in a day the people doubt in it.” I [the narrator] said to him: “May I be sacrificed for you, and if one has not fasted any days of Sha`baan, what should we do?” He (as) replied: “He makes the intention of the night of doubt, in that he is fasting from [the days] of Sha`baan. If it turns out it is [from the days] of the Month of Ramadhan it suffices for him; and if it is from [the days] of Sha`baan, it does not harm him.” I [the narrator] said: “How does a voluntary fast suffice in place of an obligatory fast?” He (as) said: “If a person fasts a day from the Month of Ramadhan voluntarily while he does not know if it is from the Month of Ramadhan, then he comes to know that it is, then it will suffice – because the obligation only transpired on the day itself.”

Source: al-Kafi, Volume 4, Page 83-84, Hadith #1; Wasaa’il al-Shia, Volume 10, Page 22-23, Hadith #8 / 12737 (See Reference One below)

وباسناده عن أحمد بن محمد بن الحسن بن الوليد، عن أبيه، عن محمد بن الحسن الصفار، عن علي بن محمد القاساني، عن القاسم بن محمد كاسولا، عن سليمان ابن داود الشاذكوني، عن عبد الرزاق، عن معمر، عن محمد بن شهاب الزهري قال: سمعت علي بن الحسين عليه السلام يقول: يوم الشك أمرنا بصيامه ونهينا عنه أمرنا ان يصومه الانسان على أنه من شعبان، ونهينا عن أن يصومه على أنه من شهر رمضان وهو لم ير الهلال
Ali ibn al-Hussain [al-Sajjad] (as) said: “We (as) have ordered to fast the day of doubt, as well as forbidding it. We have ordered the people in fasting it [with the intention of it being from the days] from Sha`ban, and forbidden to fast it [with the intention of it being from the days] of the Month of Ramadhan while he has not [yet] seen the crescent.

Source: al-Tahdheeb, Volume 4, Page 164, Hadith #463; al-Istibsaar, Volume 2, Page 82, Hadith #243; Wasaa’il al-Shia, Volume 10, Page 26-27, Hadith #4 / 12746 (See Reference One below)

It is clear one must have the intention of it being a fast other than that of it being a day of the Month of Ramadhan on a day one has doubt. In fact, if one fasts with the intention of it being a day from the Month of Ramadhan, then he will need to repeat his fast (Qadha) – even if it turns out it is Ramadhan.

محمد بن الحسن باسناده عن الحسين بن سعيد، عن محمد بن أبي عمير، عن هشام بن سالم وأبي أيوب، عن محمد بن مسلم، عن أبي جعفر عليه السلام في الرجل يصوم اليوم الذي يشك فيه من رمضان، فقال: عليه قضاؤه وإن كان كذلك
Abi Ja`far [al-Baqir] (as) was asked about a man who fasts a day in which he doubts if it is from [the days of the Month of] Ramadhan [with the intention of it being Sha`ban*]. He (as) said: “Upon him is Qadha (repeat of the fast), even if it was as such (the Month of Ramadhan).

Source: al-Tahdheeb, Volume 4, Page 182, Hadith #507; al-Istibsaar, Volume 2, Page 78, Hadith #239; Wasaa’il al-Shia, Volume 10, Page 25, Hadith #1 / 12743 (See Reference One below)

Grading: Sayed Sadiq al-Rohani says it is Authentic/Sahih (صحيح) [Fiqh al-Sadiq, Volume 12, Page 44]

* Note: We conclude this particular hadith is speaking about the one who fasts with the intention of it being a day from the Month of Ramadhan from the indications of other hadiths, such as the ones which have passed. al-Hurr al-Amili has said:

أقول: حمله الشيخ على من صامه بنية أنه من شهر رمضان
I say: al-Shaykh [al-Tusi] has attributed this to the one who fasts with the intention of it being a part of the Month of Ramadhan.

References: Wasa’il al-Shia, Volume 10, Page 25; al-Istibsaar, Volume 2, Page 79 (See Reference One below)

This is further strengthened by the following hadiths:

وباسناده عن أبي غالب الزراري، عن أحمد بن محمد، عن عبد الله بن أحمد، عن محمد بن أبي عمير، عن هشام بن سالم، عن أبي عبد الله عليه السلام قال في يوم الشك: من صامه قضاه وإن كان كذلك، يعني من صامه أنه من شهر رمضان بغير رؤية قضاه، وإن كان يوما من شهر رمضان لان السنة جاءت في صيامه على أنه من شعبان، ومن خالفها كان عليه القضاء.
Abi Abdillah [al-Sadiq] (as) said about the day of doubt: “Whoever fasts [on this day] there is Qadha (repeat of the fast), even if it was as such (the Month of Ramadhan) – meaning whoever fasts with [the intention] that it is from the Month of Ramadhan without sighting [the crescent], there is Qadha (repeat of the fast), even if it turns out it is a day of the Month of Ramadhan – because the Sunnah came in that the fast is upon the day of Sha`ban, and whoever opposes this upon him is Qadha (repeat of the fast).

Source: al-Tahdheeb, Volume 4, Page 162, Hadith #457; Wasaa’il al-Shia, Volume 10, Page 27, Hadith #5 / 12747 (See Reference One below)

Therefore, on a day you doubt which day it is – if one were to fast with the intention of it being a day from the Month of Ramadhan, he would need to repeat the fast, regardless of which day it turns out to be. If it turns out to be Ramadhan, the fast would be obligatory to repeat to make up for the obligation of Ramadhan. If it turns out to be Sha`baan, then the fast would need to be repeated to gain the reward of fasting the day of Sha`baan. Of course, this latter fast would only be recommended since the fast of Sha`baan is not obligatory. Ultimately, the ruling is that fast is null and void.

One of the reasons it may be considered forbidden is due to the saying of the Prophet of Allah (sawa):

وباسناده عن علي بن الحسن بن فضال، عن الحسين بن نصر، عن أبيه، عن أبي خالد الواسطي، عن أبي جعفر عليه السلام – في حديث – قال: قال رسول الله صلى الله عليه وآله وسلم، من الحق في رمضان يوما من غيره فليس بمؤمن بالله ولأبي
In a hadith, Abi Ja`far [al-Baqir] (as) said: “The Messenger of Allah (sawas) said whoever appended an extra day to [the Month] of Ramadhan other than it [i.e. what it should be], he is not a believer in Allah, nor in me [i.e. my Prophethood].

Source: al-Tahdheeb, Volume 4, Page 161, Hadith #454; Wasaa’il al-Shia, Volume 10, Page 27, Hadith #6 / 12748 (See Reference One below)

There are other hadiths and discussions as to the details of this, such as having the intention of “maa fi al-dhimma” or the intention of it being conditional (explained in following fatwa) which is beyond the scope of this analysis. Therefore, we refer to our righteous scholars who confirm these hadiths and give us their clear fatwas. The following is from Sayed al-Sistani (please refer to your own marja`):

1577. If one doubts whether it is the last day of Sha’ban or the first day of Ramadhan then the fast on that day is not obligatory. If however, somebody wants to observe fast on that day he cannot do so with the intention of observing the Ramadhan fast, but if he makes an intention that if it is Ramadhan then it is the Ramadhan fast and if it is not Ramadhan then it is qadha fast or some other fast like that, his fast will be valid. But it is better to observe the fast with the intention of qadha fast or some other fast, and if it is known later that it was Ramadhan then it will automatically be Ramadhan fast. And even if he makes a niyyat of a natural fast, and later it becomes known that it is Ramadhan, it will be sufficient (i.e. that fast will be counted as the Ramadhan fast).

1578. If it is doubtful whether it is the last day of Sha’ban or the first of Ramadhan, and a person observes a qadha or a Mustahab fast or some other fast on that day, and later comes to know the same day that it is the first of Ramadhan, then he should convert the intention to the Ramadhan fast.

Link: http://www.sistani.org/english/book/48/2262/

References:

(1) Wasa’il al-Shia, Volume 10

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(2) Mir’aat al-Uqool, Volume 16

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