What is the ruling regarding regurgitation (qalas) exiting the body?
Chapter on What Nullifies Purification
Al-Mughni
Book of Purification
Primary text
Regurgitation invalidates ablution if the amount is excessive, similar to blood. The consensus among the associates of Abu 'Abd Allah (Ahmad) is that if it is excessive, ablution must be repeated. The ruling for worms exiting the body is the same: if they are numerous, ablution is invalidated; if minor, it is not invalidated; the numerous amount is that which is considered excessive by one's inner sense.
Supporting text
It has been narrated from him (Ahmad) that ablution is required if the mouth is filled with regurgitation. It was also said that if it is less than half the mouth, ablution is not required. The first opinion constitutes the established Madhhab.