Intentionally eating or drinking, while aware of the fast, invalids the fast. This is regardless of whether the consumed material was something normal – such as bread and water – or not – such as glass and the sap of a tree – irrespective of whether it was a little or a lot. However, if a fasting person eats or drinks something inadvertently (sahwan), his fast will not become invalid.
2. Sexual Intercourse
Sexual intercourse invalidates a fast even if penetration is as little as the circumcised part of the penis, and even if there is no ejaculation.
Any action that results in ejaculation, causes the fast to be invalid. If a person ejaculates involuntarily, his fast does not become invalid. Also, wet dreams do not cause the fast to become invalid.
4. Ascribing false things to Allah, Prophet Muhammad (p.b.u.h & his family), and the Twelve Imams (a.s)
This is regardless of whether it was ascribed verbally, in writing, or by making a sign and suchlike. Based on obligatory precaution his fast is invalid. The same applies, based on recommended precaution, to ascribing something false to Fatima Al-Zahra (a.s) and to the other prophets and their successors. If someone quotes something as the word of Allah, Prophet Muhammad (p.b.u.h & his family), or the Twelve Imams (a.s) with the belief that it is true, and afterward he realizes that it was false, their fast does not become invalid.
5. Causing Thick Dust to Reach the Throat
On the basis of obligatory precaution, causing thick dust to reach one’s throat invalidates a fast, whether the dust is of something that is lawful (ḥalāl) to eat, such as flour, or it is of something that is unlawful (ḥarām) to eat, such as soil. The obligatory precaution is that a fasting person must not cause the smoke of cigarettes, tobacco, or something similar to reach his throat.
6. Remaining in A State of Ritual Impurity
One who intends to fast must cleanse themselves from (janābah), menstruation (ḥayḍ), or lochia (nifās) before the Fajr adhan, otherwise their fast will be invalid.
7. Applying Liquid Enema
Applying liquid enema – even if one is obliged to or for the purposes of treatment – invalidates a fast.
8. vomiting intentionally.
Whenever a fasting person intentionally vomits, his fast becomes invalid even if he vomited out of necessity or because of illness or suchlike. However, if he vomits unintentionally or involuntarily, there is no problem [and his fast remains valid].
Yet it must be acknowledged that there is no certainty that if a person conducted a valid fast, it will be accepted by Allah (s.w.t); "Verily, Allah accepts only from those who are Al-Muttaqûn (the pious)” (2), and Amir Al-Mu’mineen (a.s) stated, “How many people [who fast] are there that do not gain anything from their fast other than hunger and thirst.” (3).
Thus, there must be a deeper meaning to the reality of this worship and the method of conducting it which will be worthy of our creator accepting it. Hence, we see the sayings of Ahl Al-Bayt (a.s) regarding true fasting as abstaining every part of the body from things prohibited by Allah, including eyes, ears, tongue, etc. Imam Al-Sadiq (a.s) stated, “If you fast then your ears, eyes, hair, tongue, … should all fast.” (4)
(1) In accordance with the verdict of Sayed Al-Sistani.
(2) Al-Quran, 5:27
(3) Nahj Al-Balagha, Wisdom Word 142.
(4) Mizan Al-Hikma v2, p.1688. View the same page for more.