وَعَنْ عَمَّارِ بْنِ يَاسِرٍ رضى الله عنه
قَالَ: «مَنْ صَامَ اَلْيَوْمَ اَلَّذِي يُشَكُّ فِيهِ فَقَدْ عَصَى أَبَا اَلْقَاسِمِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ -» وَذَكَرَهُ اَلْبُخَارِيُّ تَعْلِيقًا، وَوَصَلَهُ اَلْخَمْسَةُ، وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ، وَابْنُ حِبَّانَ
Ammar ibn Yasir (RAA) narrated, ‘Whoever fasts the day of doubt he has then disobeyed Abu al-Qasim (the Prophet (sallallahu alayhi wa sallam)).’ Related by the five Imams, and Ibn Khuzaimah and Ibn Hibban graded it as Sahih.
Bulugh al-Maram 759, Book 5, Fasting, Hadith 2. 1 min read