´Silah bin Zufar said:` "We were with Ammar bin Yasir when a roasted sheep was brought and he said: 'Eat.' Someone among the people said: 'I am fasting.' So Ammar said: 'Whoever fasts on a day in which there is doubt, then he has disobeyed Abul-Qasim (pbuh)."
Hadith Referenceسنن ترمذي / كتاب الصيام عن رسول الله صلى الله عليه وسلم / 686
Hadith Gradingالألبانی:صحيح، ابن ماجة (1645) | زبیر علی زئی:(686) إسناده ضعيف /د 2334، ن 2190، جه 1645