صحیح ابن حبان
Ibn Hibban
كتاب الصوم
Book of Fasting
فصل في صوم يوم الشك - ذكر البيان بأن من صام اليوم الذي يشك فيه أمن شعبان هو أم من رمضان كان آثما عاصيا إذا كان عالما بنهي المصطفى صلى الله عليه وسلم عنه
Section on Fasting the Day of Doubt - Clarifying that knowingly fasting the day of doubt is sinful if aware of the Prophet’s prohibition
1 hadith
Hadith 3595
Sila bin Zufar narrates: We were present with Sayyiduna Ammar bin Yasir (may Allah be pleased with him) when a roasted goat was brought. He said: Eat the food. One person withdrew and said: I am fasting. Sayyiduna Ammar bin Yasir (may Allah be pleased with him) said: Whoever fasts on a day about which he is doubtful, then he has disobeyed Sayyiduna Abul Qasim (the Prophet Muhammad) (peace be upon him).