Reference: Fataawa Noor ‘alad-Darb – Question No.6422, Page 250, Volume 12
Question: When I see a reprehensible act, and I do not completely know the Islaamic ruling regarding it, then I do not say anything to the one doing it; so am I correct in doing this or not?
Response: Yes, you are correct. If a person does not know that a certain act which is taking place is [legally recognised as] a reprehensible act, then it is not permissible for him to try and put a stop to it. That is because if he was to put a stop to it – when in fact it is not legally recognised as a reprehensible act, then he has spoken about the religion of Allaah without knowledge. And to speak about the religion of Allaah without knowledge is prohibited to the extreme. Indeed, Allaah (Ta’aala) has even related it to committing shirk with Him, as He (Jalla wa ‘Alaa) has said:
However, if we consider someone told this person that this act is reprehensible, then in this case there is no harm for him to then say to the one doing the act: ‘Excuse me, you did such-and-such an act, and I have been informed that it is [legally recognised as] a reprehensible act.’ [In any case, it is better] if you were to ask about it, and be upon sound guidance’. As for a matter which the person has no knowledge whatsoever about, then it is not permissible for him to [interfere and] try and put a stop to it.