✅ Answer: Please reflect on the following narrations:

عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي جَعْفَرٍ وَ أَبِي عَبْدِ اللَّهِ قَالَ: سَأَلْتُهُمَا عَنْ رَجُلٍ مَرِضَ فَلَمْ يَصُمْ حَتَّى أَدْرَكَهُ رَمَضَانٌ آخَرُ فَقَالا إِنْ كَانَ بَرَأَ ثُمَّ تَوَانَى قَبْلَ أَنْ يُدْرِكَهُ الرَّمَضَانُ الْآخَرُ صَامَ الَّذِي أَدْرَكَهُ وَ تَصَدَّقَ عَنْ كُلِّ يَوْمٍ بِمُدٍّ مِنْ طَعَامٍ عَلَى مِسْكِينٍ وَ عَلَيْهِ قَضَاؤُهُ وَ إِنْ كَانَ لَمْ يَزَلْ مَرِيضاً حَتَّى أَدْرَكَهُ رَمَضَانٌ آخَرُ صَامَ الَّذِي أَدْرَكَهُ وَ تَصَدَّقَ عَنِ الْأَوَّلِ لِكُلِّ يَوْمٍ مُدٌّ عَلَى مِسْكِينٍ وَ لَيْسَ عَلَيْهِ قَضَاؤُهُ.

📚 Kafi Vol. 4, p. 119

Translation: Muhammad ibn Muslim said: I asked Imam Sadiq and Imam Baqir (peace be upon them both) about a person who falls ill and does not fast (in the month of Ramadan) until the next Ramadan arrives. The two Imams said: If he recovers from his illness and is lazy (and does not make up his fasts) before the next Ramadan, he should fast this Ramadan that has arrived and give one mudd of food in charity for each day (from the past Ramadan that he did not fast), and the make-up of those fasts is (still) his responsibility. But if he remains ill until the next Ramadan, he should fast this Ramadan that has arrived and give one mudd of food in charity for each day of the previous Ramadan, and making them up is not his responsibility.

عَنِ الْحَلَبِيِّ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: إِذَا كَانَ عَلَى الرَّجُلِ شَيْ ءٌ مِنْ صَوْمِ شَهْرِ رَمَضَانَ- فَلْيَقْضِهِ فِي أَيِّ شَهْرٍ شَاءَ أَيَّاماً مُتَتَابِعَةً فَإِنْ لَمْ يَسْتَطِعْ فَلْيَقْضِهِ كَيْفَ شَاءَ وَ لْيُحْصِ الْأَيَّامَ فَإِنْ فَرَّقَ فَحَسَنٌ فَإِنْ تَابَعَ فَحَسَنٌ

📚 Tahdhib Vol. 4, p. 274

Translation: Imam Sadiq (peace be upon him) said: When a person has a number of missed fasts from Ramadan, he can make them up consecutively and without a break in any month he wishes. If he cannot, he can make them up however he wishes and count the days. If he does them separately, it is good, and if he does them consecutively, it is also good.

عَنْ سُلَيْمَانَ بْنِ جَعْفَرٍ الْجَعْفَرِيِّ أَنَّهُ سَأَلَ أَبَا الْحَسَنِ الرِّضَا عَنِ الرَّجُلِ يَكُونُ عَلَيْهِ أَيَّامٌ مِنْ شَهْرِ رَمَضَانَ أَ يَقْضِيهَا مُتَفَرِّقَةً قَالَ لَا بَأْسَ بِتَفْرِقَةِ قَضَاءِ شَهْرِ رَمَضَانَ- إِنَّمَا الصِّيَامُ الَّذِي لَا يُفَرَّقُ صَوْمُ كَفَّارَةِ الظِّهَارِ وَ كَفَّارَةِ الدَّمِ وَ كَفَّارَةِ الْيَمِينِ.

📚 Man La Yahduruhu al-Faqih Vol. 2, p. 148

Translation: Sulayman al-Ja'fari asked Imam Reza (peace be upon him) about a person who owes days of Ramadan fasts, should he make them up separately and individually? The Imam said: There is no problem with making up the fasts of Ramadan separately and individually. The fasts that are not separated (and must be done consecutively) are the fast of the atonement for 'zihar' (a form of divorce), the fast of the atonement for (accidental) killing, and the fast of the atonement for an oath.

✅ From the entirety of the above narrations and others, it is clear that a person who becomes so ill in the month of Ramadan that he is unable to fast, the fast is dropped from him by divine decree, and he must break his fast. However, he is obligated to make up these fasts before the arrival of the next Ramadan. Now, if he remains ill and has an excuse until the next Ramadan, the obligation of making them up is dropped from him, but he must give one mudd of food in charity for each day. And if he recovers from his illness during the year and becomes able to make up his fasts but is lazy and negligent until the next Ramadan arrives, not only is the make-up of the fasts not dropped from him, but he must also give one mudd of food in charity for each day.

✅ Also, from the last narration, it became clear that this type of make-up fast can be performed either consecutively or separately. However, in some cases, such as the three days of atonement for an oath and in cases where the fast of 'two consecutive months' is obligatory upon a person, they must be done consecutively with specific rulings and in a specific manner, whose rulings are separate.