✅Answer: Please pay attention to the following narrations:

1 بَكْرِ بْنِ مُحَمَّدٍ الْأَزْدِيِّ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: سَأَلَهُ أَبِي وَ أَنَا أَسْمَعُ عَنْ حَدِّ الْمَرَضِ الَّذِي يَتْرُكُ الْإِنْسَانُ فِيهِ الصَّوْمَ قَالَ إِذَا لَمْ يَسْتَطِعْ أَنْ يَتَسَحَّرَ

📚 Al-Faqih, vol. 2, page 132

Bakr said: While I was listening, my father asked Imam Sadiq (peace be upon him) about the extent of illness in which a person can break his fast. The Imam said: 'When (due to the severity of the illness) he is unable to eat a sahur.'

2 مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ: قُلْتُ لِأَبِي عَبْدِ اللَّهِ مَا حَدُّ الْمَرِيضِ إِذَا نَقِهَ فِي الصِّيَامِ فَقَالَ ذَلِكَ إِلَيْهِ هُوَ أَعْلَمُ بِنَفْسِهِ إِذَا قَوِيَ فَلْيَصُمْ

📚 Al-Kafi, vol. 4, page 119

Muhammad ibn Muslim said: What is the extent for a sick person regarding fasting when he is in a period of convalescence and is recovering? (When should the recovering patient start fasting?) The Imam said: 'The decision in this matter is up to him. He knows himself best. When he regains the strength and ability (to fast), he must fast.'

3 عَنْ سَمَاعَةَ قَالَ: سَأَلْتُهُ مَا حَدُّ الْمَرَضِ الَّذِي يَجِبُ عَلَى صَاحِبِهِ فِيهِ الْإِفْطَارُ كَمَا يَجِبُ عَلَيْهِ فِي السَّفَرِ وَ مَنْ كانَ مَرِيضاً أَوْ عَلى سَفَرٍ قَالَ هُوَ مُؤْتَمَنٌ عَلَيْهِ مُفَوَّضٌ إِلَيْهِ فَإِنْ وَجَدَ ضَعْفاً فَلْيُفْطِرْ وَ إِنْ وَجَدَ قُوَّةً فَلْيَصُمْهُ كَانَ الْمَرَضُ مَا كَانَ

📚 Al-Kafi, vol. 4, page 118

Sama'a said: I asked (Imam Sadiq, peace be upon him): 'What is the extent of the illness that makes it obligatory for its owner to break the fast, just as it is obligatory for him in travel? (as Allah has said) 'Whoever is sick or on a journey...'?' The Imam said: 'He is considered trustworthy in this matter and it is left to him. So if he feels weakness and inability, he must break his fast, and if he finds strength and ability (to fast), he must fast, whatever his illness may be!'

4 عَلِيُّ بْنُ جَعْفَرٍ عَنْ أَخِيهِ مُوسَى بْنِ جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنْ حَدِّ مَا يَجِبُ عَلَى الْمَرِيضِ تَرْكُ الصَّوْمِ قَالَ كُلُّ شَيْ ءٍ مِنَ الْمَرَضِ أَضَرَّ بِهِ الصَّوْمُ فَهُوَ يَسَعُهُ تَرْكُ الصَّوْمِ

📚 Masa'il Ali ibn Ja'far, page 171

Ali ibn Ja'far said: I asked Musa ibn Ja'far (peace be upon him) about the extent of illness that makes it obligatory for one to break the fast. The Imam said: 'Any illness that fasting harms, he has permission and a dispensation to break the fast in that case.'

5 عَمَّارِ بْنِ مُوسَى عَنْ أَبِي عَبْدِ اللَّهِ فِي الرَّجُلِ يَجِدُ فِي رَأْسِهِ وَجَعاً مِنْ صُدَاعٍ شَدِيدٍ هَلْ يَجُوزُ لَهُ الْإِفْطَارُ قَالَ إِذَا صُدِّعَ صُدَاعاً شَدِيداً وَ إِذَا حُمَّ حُمَّى شَدِيدَةً وَ إِذَا رَمِدَتْ عَيْنَاهُ رَمَداً شَدِيداً فَقَدْ حَلَّ لَهُ الْإِفْطَارُ

📚 Al-Kafi, vol. 4, page 118

Imam Sadiq (peace be upon him) was asked about a person who has a severe headache, is it permissible for him to break the fast? The Imam said: 'When he gets a severe headache, or a severe fever, or a severe eye pain, it is permissible for him to break the fast.'

✅ In the above narrations, it is observed that a sick person who, due to weakness, inability, and the severity of pain, is unable to eat a sahur and fast, must break his fast. The decision is left to the person himself because everyone knows himself best.

✅ In the fourth narration, the harmfulness of fasting for a person's illness is also mentioned as a criterion for the permissibility of not fasting. This harmfulness, in whatever way it is determined with certainty, makes no difference, even if it is by a doctor's diagnosis. However, it should be noted that there should be no excuses or negligence, and fasting must truly be harmful to that illness.

✅ As for the ruling on a sick person whose duty is to break the fast but who fasts:

6 الزُّهْری عن عَلِيِّ بْن الْحُسَيْن في حَدِيث قَالَ:و أَمَّا نَحْنُ فَنَقُولُ يُفْطِرُ فِي الْحَالَيْن جَمِيعاً فَإِنْ صَامَ فِي حَالِ السَّفَرِ أَوْ فِي حَالِ الْمَرَضِ فَعَلَيْهِ الْقَضَاءُ

📚 Al-Kafi, vol. 4, page 86

Imam Sajjad (peace be upon him) said: '...We say that a person in both cases (travel and illness) should break his fast, and whoever fasts while traveling or sick must make up for it!'

✅ In the following posts, also read some topics related to those who are unable to fast:

https://feghh14.com/en/360

https://feghh14.com/en/433

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ

وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ