Yahya bin Abi Kathir يحيى بن أبي كثير الطائي · Fasting (Kitab Al-Siyam)

AbuIshaq reported on the authority of Silah: We were with Ammar on the day when the appearance of the moon was doubtful. (The meat of) goat was brought to him. Some people kept aloof from (eating) it. Ammar said: He who keeps fast on this day disobeys AbulQasim (i.e. the Prophet) (ﷺ).

The Prophet (ﷺ) said: Snuff up water freely unless you are fasting.

The Prophet (ﷺ) said: A man who cupped and a man who has himself cupped broke their fast. The narrator Shayban said in his version: AbuQilabah told me that AbuAsma' ar-Rahbi told him that Thawban, the client of the Messenger of Allah (ﷺ), told him that he heard the Prophet (ﷺ) say this.

The Prophet (ﷺ) said: if one has a sudden attack of vomiting while one is fasting, no atonement is required of him, but if he vomits intentionally he must make atonement.