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).