The World Federation One Stop Fiqh

Ruling 1579

If someone intentionally ascribes to Allah the Exalted, the Most Noble Prophet (Ṣ), or the Infallible Imams (ʿA) something that has been fabricated by some other person, then as an obligatory precaution his fast becomes invalid. However, if he simply narrates from the person who fabricated the falsehood without knowing it to be false, there is no problem [and his fast is valid].