Fasting in the month of Ramadan is compulsory on every Muslim adult. The Arabic word Sawm literally means ‘to refrain’, but as an Islamic term, it means refraining from food, drinks and sexual activity from dawn to sunset.
According to Sheikh Bakera Ally of the Kigali main Mosque, there are nine acts which invalidate fast:
Eating and drinking: If a person eats or drinks something intentionally, while being conscious of fasting, his fast becomes void, irrespective of whether the thing which he ate or drank was usually eaten or drunk.
Sexual intercourse: Sexual intercourse invalidates the fast, even if the penetration is as little as the tip of the male organ, and even if there has been no ejaculation.
Masturbation: If a person, who is observing a fast, masturbates, his fast becomes void but if semen is discharged from the body of a person involuntarily, his fast does not become void.
Ascribing lies to Allah and his prophet: If a person who is fasting, intentionally ascribes something false to Allah and the Prophet, verbally or in writing or by making a sign, his fast becomes void, even if he may at once retract and say that he has uttered a lie or may repent for it.
Letting dust reach one’s throat: On the basis of obligatory precaution, allowing thick dust to reach one’s throat makes fasting void, whether the dust is of something which is halal to eat, like flour, or of something which is haraam to consume like dust or earth. Allowing thin dust to reach one’s throat will invalidate the fast.
Remaining in Janabat or Haidh or Nifas till Fajr time: If a person in janabat does not take Ghusi intentionally till the time of Fajr prayers, his/her fast becomes void.
Immersing one’s head in water: If a fasting person intentionally immerses his entire head in the water, his fast is known to be void, even if the rest of his body remains out of water.
But this act does not invalidate the fast; it is a Makrooh act, and as a measure of precaution, should be avoided. If a person immerses half of his head in the water once and the other half the second time, his fast is not affected.
Vomiting: If a fasting person vomits his fast becomes void, though he may have been obliged to do so, on the account of sickness. However, the fast does not become void, if one vomits forgetfully or involuntarily.
Enema: If liquid enema is taken by a fasting person, his fast becomes void even if he is obliged to take it for the sake of treatment.
These are some of the things that can invalidate ones fast. However, if a person due to utter ignorance of the rules, or due to reliance upon some authority which he thought was genuine, unhesitatingly commits an act which invalidates the fast, his fast will not be void, except in the case of eating and sexual intercourse.