✅ Answer: Consider the following narrations:

1 عَنْ جَعْفَرِ بْنِ عِيسَى أَخُوهِ قَالَ: سَأَلْتُ الرِّضَا عَنْ صَوْمِ يَوْمِ عَاشُورَاءَ وَ مَا يَقُولُ النَّاسُ فِيهِ فَقَالَ عَنْ صَوْمِ ابْنِ مَرْجَانَةَ تَسْأَلُنِي ذَلِكَ يَوْمٌ صَامَهُ الْأَدْعِيَاءُ مِنْ آلِ زِيَادٍ لِقَتْلِ الْحُسَيْنِ وَ هُوَ يَوْمٌ يَتَشَاءَمُ بِهِ آلُ مُحَمَّدٍ وَ يَتَشَاءَمُ بِهِ أَهْلُ الْإِسْلَامِ وَ الْيَوْمُ الَّذِي يَتَشَاءَمُ بِهِ أَهْلُ الْإِسْلَامِ- لَا يُصَامُ وَ لَا يُتَبَرَّكُ بِهِ وَ يَوْمُ الْإِثْنَيْنِ يَوْمُ نَحْسٍ قَبَضَ اللَّهُ فِيهِ نَبِيَّهُ وَ مَا أُصِيبَ آلُ مُحَمَّدٍ إِلَّا فِي يَوْمِ الْإِثْنَيْنِ- فَتَشَاءَمْنَا بِهِ وَ تَبَرَّكَ بِهِ عَدُوُّنَا وَ يَوْمُ عَاشُورَاءَ قُتِلَ الْحُسَيْنُ وَ تَبَرَّكَ بِهِ ابْنُ مَرْجَانَةَ- وَ تَشَاءَمَ بِهِ آلُ مُحَمَّدٍ فَمَنْ صَامَهُمَا أَوْ تَبَرَّكَ بِهِمَا لَقِيَ اللَّهَ تَبَارَكَ وَ تَعَالَى مَمْسُوخَ الْقَلْبِ وَ كَانَ مَحْشَرُهُ مَعَ الَّذِينَ سَنُّوا صَوْمَهُمَا وَ التَّبَرُّكَ بِهِمَا.

📚 Al-Kafi, Vol. 4, p. 146

Ja’far ibn Isa says: I asked Imam Reza (peace be upon him) about fasting on the day of Ashura and what people say about it;

The Imam said: Are you asking me about fasting on the day of the son of Marjaneh (i.e., Ubaydullah ibn Ziyad, may Allah curse him)?!

That is the day when the illegitimate offspring of the Ziyad family fasted due to the killing of Imam Husayn (peace be upon him), and it is a day that the family of Muhammad (peace be upon them all) and the people of Islam consider inauspicious and unfortunate. A day considered inauspicious by Muslims is not a day for fasting or seeking blessings!

And fasting on Monday is the day when Allah took the soul of His Prophet, and the family of Muhammad has not been afflicted with calamity except on a Monday. Thus, we consider it inauspicious and unfortunate, while our enemies seek blessings in it. Ashura is the day when Husayn (peace be upon him) was killed, and the son of Marjaneh (may Allah curse him) sought blessings in it, while the family of Muhammad (peace be upon them) considered it inauspicious and unfortunate. So, whoever fasts or seeks blessings on these two days (i.e., Ashura and Monday) will meet Allah the Exalted with a transformed heart and will be resurrected with those who established the tradition of fasting on this day and sought blessings in these two days!

2 عَنْ عُقْبَةَ بْنِ بَشِيرٍ الْأَزْدِيِّ قَالَ: جِئْتُ إِلَى أَبِي جَعْفَرٍ يَوْمَ الْإِثْنَيْنِ فَقَالَ كُلْ فَقُلْتُ إِنِّي صَائِمٌ فَقَالَ وَ كَيْفَ صُمْتَ قَالَ قُلْتُ: لِأَنَّ رَسُولَ اللَّهِ وُلِدَ فِيهِ فَقَالَ أَمَّا مَا وُلِدَ فِيهِ فَلَا تَعْلَمُونَ وَ أَمَّا مَا قُبِضَ فِيهِ فَنَعَمْ ثُمَّ قَالَ فَلَا تَصُمْ وَ لَا تُسَافِرْ فِيهِ.

📚 Al-Khisal, p. 385, Hadith 66

Uqba ibn Bashir Azdi says: I came to Imam Baqir (peace be upon him) on a Monday. The Imam said: Eat (food)! I said: I am fasting!

The Imam said: On what basis are you fasting?! I said: Because the Messenger of Allah (peace be upon him and his family) was born on this day!

The Imam said: You have no knowledge that the Prophet (peace be upon him and his family) was born on this day, but it is true that he passed away on this day!

Then he said: Do not fast on it, and do not travel on it!

3 عَنِ الزُّهْرِيِّ عَنْ عَلِيِّ بْنِ الْحُسَيْنِ قَالَ: وَ أَمَّا الصَّوْمُ الَّذِي يَكُونُ صَاحِبُهُ فِيهِ بِالْخِيَارِ فَصَوْمُ يَوْمِ الْجُمُعَةِ وَ الْخَمِيسِ وَ الْإِثْنَيْنِ

📚 Al-Faqih, Vol. 2, p. 77

Imam Sajjad (peace be upon him) said in a narration: As for voluntary fasting, which the person has a choice in, it includes the days of Friday, Thursday, and Monday...

✅ Important Note: This narration appears in Al-Kafi, Vol. 4, p. 85, and Al-Tahdhib, Vol. 4, p. 296, among others, but Monday is not mentioned in them!

4 عَنْ أَبِي بَصِيرٍ قَالَ: سَأَلْتُ أَبَا عَبْدِ اللَّهِ عَنْ صَوْمِ السُّنَّةِ فَقَالَ صِيَامُ ثَلَاثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ الْخَمِيسِ وَ الْأَرْبِعَاءِ وَ الْخَمِيسِ يَذْهَبُ بِبَلَابِلِ الْقَلْبِ وَ وَحَرِ الصَّدْرِ الْخَمِيسِ وَ الْأَرْبِعَاءِ وَ الْخَمِيسِ وَ إِنْ شَاءَ الْإِثْنَيْنَ وَ الْأَرْبِعَاءَ وَ الْخَمِيسَ- وَ إِنْ شَاءَ صَامَ فِي كُلِّ عَشَرَةٍ يَوْماً فَإِنَّ ذَلِكَ ثَلَاثُونَ حَسَنَةً وَ إِنْ أَحَبَّ أَنْ يَزِيدَ عَلَى ذَلِكَ فَلْيَزِدْ.

📚 Al-Tahdhib, Vol. 4, p. 303

Abu Basir says: I asked Imam Sadiq (peace be upon him) about voluntary fasting; the Imam said: Fasting three days each month: Thursday (first of the month), Wednesday (middle of the month), and Thursday (end of the month) removes whispers of the heart, hatred, anger, and deceit from the chest. These are Thursday, Wednesday, and Thursday (from the beginning, middle, and end of each month). If one wishes, they may fast on Monday, Wednesday, and Thursday, or if they wish, they may fast one day every ten days, and if they like, they may add to this!

✅ From the above narrations and others, it is clear that the Messenger of Allah (peace be upon him and his family) passed away on a Monday. Therefore, seeking blessings, traveling, or fasting on this day as a tradition, or believing it to be the Prophet’s birthday, is prohibited. Thus, fasting on this day is not a recommended practice, and even the notion of it being optional, based on narration 3 , is not certain due to the absence of Monday in the narrations of Al-Kafi, Al-Tahdhib, and others.

✅ The permission to choose Monday for the three-day monthly fast in narration 4 is, firstly, not based on seeking blessings or the false belief in the Prophet’s birth on this day, and secondly, this is mentioned only in this single narration. In numerous other narrations, the days specified for the three-day monthly fast are Thursday at the beginning of the month, Wednesday in the middle, and Thursday at the end, or vice versa. This is merely a concession in this single narration for choosing Monday for the three-day monthly fast.

✅ Narrations stating that the Messenger of Allah (peace be upon him and his family) fasted on Mondays and Thursdays because deeds are presented to the Lord of the Worlds on these days are general narrations and not reliable for Shia practice.

✅ If Monday coincides with days like Eid al-Ghadir, Dhu al-Hijjah, or the months of Rajab or Sha’ban, this does not affect the validity of fasting as a recommended practice on those days, and fasting is observed with the specific intention for those occasions.

✅ The above pertains to voluntary and recommended fasting and does not apply to obligatory fasting, missed fasts, Ramadan fasting, expiatory fasting, or similar. If these types of fasting coincide with a Monday, there is no prohibition or issue in the narrations. The prohibition only concerns the specific voluntary fasting on Monday based on the belief that it is the Prophet’s birthday or an auspicious day, as according to Shia narrations, Monday is the day of the Prophet’s martyrdom (peace be upon him and his family) and the subsequent usurpation of the caliphate:

5 عَنْ أَبِي أَيُّوبَ الْخَرَّازِ أَنَّهُ قَالَ: أَرَدْنَا أَنْ نَخْرُجَ فَجِئْنَا نُسَلِّمُ عَلَى أَبِي عَبْدِ اللَّهِ فَقَالَ كَأَنَّكُمْ طَلَبْتُمْ بَرَكَةَ الْإِثْنَيْنِ قُلْنَا نَعَمْ قَالَ فَأَيُّ يَوْمٍ أَعْظَمُ شُؤْماً مِنْ يَوْمِ الْإِثْنَيْنِ- فَقَدْنَا فِيهِ نَبِيَّنَا وَ ارْتَفَعَ الْوَحْيُ عَنَّا لَا تَخْرُجُوا يَوْمَ الْإِثْنَيْنِ وَ اخْرُجُوا يَوْمَ الثَّلَاثَاءِ.

📚 Al-Faqih, Vol. 2, p. 267

Abu Ayyub says: We intended to travel and came to bid farewell to Imam Sadiq (peace be upon him).

The Imam said to us: It seems you are seeking blessings from Monday (by choosing it for travel)?!

We said: Yes! The Imam said: What day is more inauspicious than Monday, when we lost our Prophet and revelation was cut off from us?! Do not travel on Monday; travel on Tuesday!

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ