Question
What is the ruling on a fasting person who vomits a mouthful and then induces vomiting intentionally?
Answer
If he vomits intentionally or a mouthful or more of it, then his fast is invalidated, and he must make up for it, as long as the original amount is a mouthful. See Al-Tahbih 1: 325-326, and Al-Radd Al-Muhtar 2: 111.