Is the writer obliged to point out his disagreement or doubt concerning the authenticity of what he quotes from scholars, or does the responsibility lie with the original author of the statement?

The Prophet, peace and blessings be upon him, established the principle: "Religion is an-naseehah (sincerity/advice)." This includes sincerity/advice towards Allah, His Book, His Messenger, the leaders of the Muslims, and their common folk. A writer who transmits an error without clarification is remiss in offering advice, especially if the error is a universally agreed-upon falsehood or contradicts a text or a consensus, because it may lead the reader astray. This is considered a reprehensible act (munkar) that must be denounced by hand, tongue, or heart. If the writer is unable to denounce it, it is not permissible for him to transmit it in the first place, nor is it permissible to delay clarification beyond the time of need.