✅ Answer: Refer to the following narrations:

1⃣عَنْ أَبِي جَعْفَرٍ فِي قَوْلِ اللَّهِ عَزَّوَجَلَّ الَّذِينَ يَذْكُرُونَ اللَّهَ قِياماً وَ قُعُوداً وَ عَلى جُنُوبِهِمْ [۳] قَالَ الصَّحِيحُ يُصَلِّي قَائِماً وَ قُعُوداً الْمَرِيضُ يُصَلِّي جَالِساً وَ عَلَى جُنُوبِهِمْ الَّذِي يَكُونُ أَضْعَفَ مِنَ الْمَرِيضِ الَّذِي يُصَلِّي جَالِساً

📚 Al-Kafi, Vol. 3, p. 411

[3]: Aal-Imran 3:191.

Imam Baqir (peace be upon him) explained the verse of Allah, who says: 'Those who remember Allah standing, sitting, and lying on their sides,' stating: The healthy person prays standing, and 'Qoodan' (sitting) is for the sick person who prays while seated, and 'on their sides' refers to someone weaker and more incapacitated than a person who prays seated due to illness.

2⃣ عَنِ الْحَلَبِيِّ عَنْ أَبِي عَبْداللَّه قَالَ: سَأَلْتُهُ عَنِ الْمَرِيضِ إِذَا لَمْ يَسْتَطِعِ الْقِيَامَ وَ السُّجُودَ قَالَ يُومِئُ بِرَأْسِهِ إِيمَاءً وَ أَنْ يَضَعَ جَبْهَتَهُ عَلَى الْأَرْضِ أَحَبُّ إِلَيَّ

📚 Al-Kafi, Vol. 3, p. 410

Halabi said: I asked Imam Sadiq (peace be upon him) about a sick person who cannot stand or prostrate. He said: The person should pray by indicating (i.e., perform bowing and prostration with gestures), and if they can place their forehead on the ground, it is more beloved to me.

3⃣عَنْ إِبْرَاهِیمَ بْنِ أَبِی زِیَادٍ الْكَرْخِيِّ قَالَ: قُلْتُ لِأَبِي عَبْدِ اللَّهِ رَجُلٌ شَيْخٌ لَا يَسْتَطِيعُ الْقِيَامَ إِلَى الْخَلَاءِ وَ لَا يُمْكِنُهُ الرُّكُوعُ وَ السُّجُودُ فَقَالَ لِيُومِئْ بِرَأْسِهِ إِيمَاءً وَ إِنْ كَانَ لَهُ مَنْ يَرْفَعُ الْخُمْرَةَ فَلْيَسْجُدْ فَإِنْ لَمْ يُمْكِنْهُ ذَلِكَ فَلْيُومِئْ بِرَأْسِهِ نَحْوَ الْقِبْلَةِ إِيمَاءً

📚 Al-Tahdhib, Vol. 3, p. 307

Karkhi said: I asked Imam Sadiq (peace be upon him) about an elderly man who cannot go to the restroom, and performing bowing and prostration is not possible for him. The Imam said: He should perform bowing and prostration by nodding his head, and if someone is available to raise the prayer mat for him, he should prostrate. If this is not possible, he should indicate with his head toward the Qibla.

4⃣ عَنْ عَلِيٍّ أَنَّ رَسُولَ اللَّهِ سُئِلَ مَتَى يُصَلِّي الْمَرِيضُ قَاعِداً قَالَ إِذَا لَمْ يَسْتَطِعْ أَنْ يَقْرَأَ فَاتِحَةَ الْكِتَابِ وَ ثَلَاثَ آيَاتٍ قَائِماً فَلْيُصَلِّ قَاعِداً

📚 Al-Ja'fariyyat, p. 47

Imam Ali (peace be upon him) said: The Prophet (peace be upon him) was asked: When should a sick person pray while sitting? He replied: When they cannot recite Surah Al-Fatiha and three verses of the Quran while standing!

5⃣عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنِ الْمَرِيضِ كَيْفَ يَسْجُدُ فَقَالَ عَلَى خُمْرَةٍ أَوْ عَلَى مِرْوَحَةٍ أَوْ عَلَى سِوَاكٍ يَرْفَعُهُ إِلَيْهِ هُوَ أَفْضَلُ مِنَ الْإِيمَاءِ

📚 Al-Faqih, Vol. 1, p. 362

Zurarah said: I asked Imam Baqir (peace be upon him) how a sick person should prostrate. He said: On a prayer mat (straw mat), or on a straw fan, or on a miswak stick that they raise toward themselves, and this is better than simply gesturing for prostration!

6⃣عَنْ مُعَاوِيَةَ بْنِ مَيْسَرَةَ أَنَّ سِنَاناً سَأَلَ أَبَا عَبْداللَّهِ عَنِ الرَّجُلِ يَمُدُّ إِحْدَى رِجْلَيْهِ بَيْنَ يَدَيْهِ وَ هُوَ جَالِسٌ قَالَ لَا بَأْسَ وَ لَا أَرَاهُ إِلَّا قَالَ فِي الْمُعْتَلِّ وَ الْمَرِيضِ

📚 Al-Kafi, Vol. 3, p. 411

Mu'awiya bin Misrah said: Sinan asked Imam Sadiq (peace be upon him) about a person who, while praying seated, extends one leg in front of them. The Imam said: There is no problem with this. The narrator said: This was said about an ill or disabled person!

✅ Based on the above narrations and others, special instructions have been designated for a person who is unable to stand, bow, or prostrate in prayer.

However, it is important to note that these instructions are applicable to all prayers and are not exclusive to obligatory (performance) prayers. Therefore, a person who has missed prayers from their healthy days can still perform their missed prayers in a manner consistent with how they are required to pray during their illness.

✅ Let us remember our master Imam al-Zamana (peace be upon him) more, and pray more for the hastening of his appearance:

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