Al-Kāfi

Hadith 444
fasting
2ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ هَارُونَ بْنِ مُسْلِمٍ عَنْ مَسْعَدَةَ بْنِ صَدَقَةَ عَنْ أَبِي عَبْدِ الله عَنْ آبَائِهِ (عَلَيْهِم السَّلاَم) أَنَّ عَلِيّاً صَلَوَاتُ الله عَلَيْهِ سُئِلَ عَنِ الذُّبَابِ يَدْخُلُ حَلْقَ الصَّائِمِ قَالَ لَيْسَ عَلَيْهِ قَضَاءٌ لأَنَّهُ لَيْسَ بِطَعَامٍ.
2. Ali ibn Ibrahim has narrated from Harun ibn Muslim Mas’adah ibn Sadaqah who has said the following: “Abu ‘Abd Allah (a.s.), has narrated from his ancestors who have said that Ali (a.s.), upon being asked about a fly entering the throat of a fasting person, said, ‘There is no Qada’ (compensatory fast) on him because it is not food.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī