سَأَلْتُ أَبَا عَبْدِ اللَّهِ ع مَا حَدُّ الْمَرَضِ الَّذِي يُفْطِرُ فِيهِ الصَّائِمُ وَ يَدَعُ الصَّلَاةَ مِنْ قِيَامٍ فَقَالَ بَلِ الْإِنْسانُ عَلى نَفْسِهِ بَصِيرَةٌ وَ هُوَ أَعْلَمُ بِمَا يُطِيقُهُ.
"I asked Abu Abdullah (as) about the extent of illness that permits a fasting person to break their fast and to pray sitting instead of standing. Imam (as) said: 'Indeed, man is a witness over himself' (Surah Al-Qiyamah 75:14), and he knows best what he can bear."