159. hadíth
وَ سَأَلَ بَشِيرٌ اَلنَّبَّالُ أَبَا عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ: عَنْ صَوْمِ يَوْمِ اَلشَّكِّ فَقَالَ «صُمْهُ فَإِنْ كَانَ مِنْ شَعْبَانَ كَانَ تَطَوُّعاً وَ إِنْ كَانَ مِنْ شَهْرِ رَمَضَانَ فَيَوْمٌ وُفِّقْتَ لَهُ».
Bashir al-Nabbal asked Abu Abdullah (a.s) about fasting on the day of doubt. Imam (a.s) said: "Fast it. If it turns out to be from Sha'ban, it is a voluntary fast, and if it turns out to be from Month of Ramadan, then it is a day you were fortunate to have fasted."