Ruling 1640 — Fasting (Ṣawm)

If a fasting person burps and something comes up in his mouth, then based on obligatory precaution, if he intentionally swallows it, his fast is invalid and he must keep a qaḍāʾ fast and give kaffārah. If eating that thing is unlawful – for example, when burping, blood or some food-like substance that has lost the form of food reaches his mouth and he intentionally swallows it – then it is better that he give the ‘total kaffārah’ [as defined in Ruling 1635].