Al-Tirmidhi narrated on the authority of Ammar bin Yasser, who said: Whoever fasts on the day of doubt has disobeyed Abu Al-Qasim

He said: This is a good and authentic hadith. The majority of scholars agree that it is forbidden to fast on the day of doubt, given that it is part of Ramadan, but they disagreed. In investigating his fasting as voluntary, some of them disliked it and some permitted it. As for the hadith of Ammar, according to me, it is not a text and is a matter raised to the Messenger of God, may God’s prayers and peace be upon him. Rather, it is possible that it was based on the opinion of Ammar, and it is possible that it was based on a report on the authority of the Prophet, may God’s prayers and peace be upon him, and some of them said that he fasted it. Although it is part of Ramadan, then it is proven that it is part of Ramadan, it suffices.