The Official Website of Grand Ayatollah Makarem Shirazi

According to the obligatory precaution, if a fasting person tells a lie and ascribes it to Allah or the divinely sent Prophets or the infallible Imams, their fasting will be invalidated. And it does not matter whether they say such a lie verbally, write it, indicate it through sign language or convey it through any other means. Even if someone recites the Qur'an incorrectly and ascribes that to Allah, their fasting will be invalidated. If one wants to relate some saying which he is not sure whether it is truly from Allah, the Prophets or the Infallibles or not, they must mention exactly who they heard it from or what book they read it in. But if one is sure that some saying is a lie and not the words of Allah, the Prophets or the Infallibles, they must not relate it even with mentioning the source. But if the words of one infallible Imam is mistakenly ascribed to another Imam, it will not invalidate the fasting. Sometimes one says something which they believe is true but later realizes that it was not. In such cases, their fasting is valid. However, if one ascribes what he considers to be a lie to Allah, the Prophets or the Infallibles, but later realizes that they have actually said such a thing, their fasting will still be problematic. If a fasting person intentionally teaches religious laws incorrectly to people and they mean to ascribe those laws to Allah or to the Prophet, they have both committed a prohibited act and have invalidated their fasting. But if they intended to ascribe those laws as a ruling to A Mujtahid, or they had been unsure about it, and later realized that it was not correct, their fasting will be valid. But they have committed a prohibited act. In addition to ascribing laws to Allah, ascribing partners to Allah will also invalidate fasting. In general, such acts are both prohibited and the invalidators of fasting. Therefore, if someone commits them, they must repent for their sin, but their repentance will not make up for their void fasting.