✅Answer: Please pay attention to the following narrations:

1 الْحَسَن بْنِ رَاشِد قال: قُلْتُ لِأَبِي عَبْداللَّه الْحَائِضُ تَقْضِي الصَّلَاةَ قَالَ لَا قُلْتُ تَقْضِي الصَّوْمَ قَالَ نَعَمْ قُلْتُ مِنْ أَيْنَ جَاءَ هَذَا قَالَ إِنَّ أَوَّلَ مَنْ قَاسَ إِبْلِيسُ

📚 Al-Kafi, vol. 3, p. 104

Hasan ibn Rashid said: I said to Imam Sadiq, peace be upon him: Does a menstruating woman make up for the prayer? He said: No! I said: Does she make up for the fast? He said: Yes! I said: Where does this come from?! He said: Indeed, the first one who made an analogy was Iblis!

2 عقبة بن خالد عن أَبِي عَبْداللَّه في رَجُلٍ مَرِضَ فِي شَهْرِ رَمَضَانَ فَلَمَّا بَرَأَ أَرَادَ الْحَجَّ كَيْفَ يَصْنَعُ بِقَضَاءِ الصَّوْمِ قَالَ إِذَا رَجَعَ فَلْيَصُمْهُ [فلیقضه]

📚 Al-Kafi, vol. 4, p. 121

Uqbah ibn Khalid said: Imam Sadiq, peace be upon him, was asked about a person who falls ill in the month of Ramadan and when he recovers from the illness, he intends to go on Hajj, what should he do about his missed fasts? He said: When he returns, he should fast and make them up!

3 عبداللَّه بْنِ سِنَانٍ عَنْ أَبِي عَبْداللَّه في حَدِيثٍ قَالَ: إِنَّ اللَّهَ قَدْ رَخَّصَ لِلْمُسَافِرِ فِي الْإِفْطَارِ وَ التَّقْصِيرِ وَ أَوْجَبَ عَلَيْهِ قَضَاءَ الصِّيَامِ وَ لَمْ يُوجِبْ عَلَيْهِ قَضَاءَ تَمَامِ الصَّلَاةِ وَ السُّنَّةُ لَا تُقَاسُ

📚 Faqih, vol. 2, p. 143

Imam Sadiq, peace be upon him, said: Indeed, Allah has given the traveler permission to break the prayer and break the fast and has made making up the fast obligatory on him, but has not made making up the completion of the prayer obligatory on him, and the tradition cannot be analogized!

✅ According to multiple narrations, in various cases, a person is obligated to completely make up for the fasts that are due on him because of menstruation, illness, travel, and so on.

However, if he has a doubt about their number, he can usually consider a maximum number for them, and based on some general principles mentioned in the narrations, including the principle of caution and the principle of building upon certainty, and due to the absence of a specific text, he should make up the number of fasts for which he is certain that he has completely fulfilled his duty.

And to understand the basis of this action, he should pay attention to the following narrations and the like:

4 عَنِ الرِّضَا أَنَّ أَمِيرَ الْمُؤْمِنِينَ قَالَ لِكُمَيْلِ بْنِ زِيَادٍ أَخُوكَ دِينُكَ فَاحْتَطْ لِدِينِكَ بِمَا شِئْتَ

📚 Amali Al-Tusi, vol. 1, p. 109

Imam Ridha, peace be upon him, said: Amir al-Mu'minin, peace be upon him, said to Kumayl ibn Ziyad: Your brother is your religion, so be cautious about whatever you want for your religion!

5 عبدالرحمن بن الْحَجَّاج قال: سَأَلْتُ أَبَا الْحَسَن عَنْ رَجُلَيْن أَصَابَا صَيْداً وَ هُمَا مُحْرِمَانِ الْجَزَاءُ بَيْنَهُمَا أَوْ عَلَى كُلِّ وَاحِدٍ مِنْهُمَا جَزَاءٌ قَالَ لَا بَلْ عَلَيْهِمَا أَنْ يَجْزِيَ كُلُّ وَاحِدٍ مِنْهُمَا الصَّيْد...فَقَال إِذَا أَصَبْتُمْ مِثْلَ هَذَا فَلَمْ تَدْرُوا فَعَلَيْكُمْ بِالاحْتِيَاطِ حَتَّى تَسْأَلُوا عَنْهُ فَتَعْلَمُوا

📚 Al-Kafi, vol. 4, p. 391

Imam Kazim, peace be upon him, said about two people in 'ihram' who had hunted a prey and did not know whether both of them had to pay the atonement or one of them: When you are afflicted with cases like this and you do not know, it is incumbent upon you to be cautious until you ask about it and gain knowledge.

6 إسحاق بن عمار قال: قال لِي أَبُو الْحَسَنِ الْأَوَّلُ إِذَا شَكَكْتَ فَابْنِ عَلَى الْيَقِينِ قَالَ قُلْتُ: هَذَا أَصْلٌ قَالَ نَعَمْ

📚 Faqih, vol. 1, p. 351

Ishaq ibn Ammar said: Imam Kazim, peace be upon him, said to me: When you have a doubt, build upon certainty! I said: Is this a principle? He said: Yes!

6 زرارة عن أبي جعفر قال: لَا يَنْقُضُ الْيَقِينَ أَبَداً بِالشَّكِّ و لَكِنْ يَنْقُضُهُ بِيَقِينٍ آخَرَ

📚 Tahdheeb, vol. 1, p. 8

Imam Baqir, peace be upon him, said: A person never breaks certainty with a doubt, but he breaks it with another certainty!

7 عنوان الْبَصْرِي عن أبي عبداللَّه جعفر بن محمد يقول فيه...إِيَّاكَ أَنْ تَعْمَلَ بِرَأْيِكَ شَيْئاً و خُذْ بِالاحْتِيَاطِ في جَمِيعِ أُمُورِكَ ما تَجِدُ إِلَيْهِ سَبِيلًا

📚 Wasa'il al-Shi'ah, vol. 27, p. 171

Imam Sadiq, peace be upon him, said to 'Unwan al-Basri: ... and beware of acting upon anything from your own opinion, and in all your affairs in which you find a way to caution, act with caution!

✅ So he should fast the number that he is certain that he has completely fulfilled his duty, and therefore he should choose the maximum amount and fast. If Allah wills.

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ

وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ