What is the ruling regarding someone whose gums bled during Dhuhr prayer after using a miswak, and who involuntarily swallowed some of it?

The duty was not to swallow the blood but to expel it into a tissue. Since the swallowing was unintentional, the fast is valid. However, if it was intentional, the day must be made up. Ibn Qudamah stated that swallowing blood or phlegm (qals) invalidates the fast, even if it is a small amount, because the mouth is considered like the external (visible) part of the body, and only saliva is excused.