Chapter on Fasting on the Day of Doubt
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 16
وَ رَوَى صَفْوَانُ بْنُ يَحْيَى عَنِ اَلْعِيصِ بْنِ اَلْقَاسِمِ قَالَ: سَأَلْتُ أَبَا عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ عَنْ قَوْمٍ أَسْلَمُوا فِي شَهْرِ رَمَضَانَ وَ قَدْ مَضَى مِنْهُ أَيَّامٌ هَلْ عَلَيْهِمْ أَنْ يَصُومُوا مَا مَضَى مِنْهُ أَوْ يَوْمَهُمُ اَلَّذِي أَسْلَمُوا فِيهِ فَقَالَ «لَيْسَ عَلَيْهِمْ قَضَاءٌ وَ لاَ يَوْمُهُمُ اَلَّذِي أَسْلَمُوا فِيهِ إِلاَّ أَنْ يَكُونُوا أَسْلَمُوا فِيهِ قَبْلَ طُلُوعِ اَلْفَجْرِ ».
Safwan ibn Yahya narrated from Al-'Is ibn al-Qasim, who said: "I asked Abu Abdullah عليه السلام about a group of people who converted to Islam during the Month of Ramadan after some days had passed. Are they required to fast the days that have passed, or the day they embraced Islam? Imam عليه السلام said: 'They are not required to make up the missed days or to fast on the day they embraced Islam, unless they embraced Islam before the break of dawn on that day.'"
- Ṣaḥīḥ al-Faqīh