Knowingly inventing a Prophetic attribution is an exceptionally grave major sin and entails *fisq*; such a fabricator's reports lose their evidentiary standing. According to the majority position transmitted by al-Nawawī, **the act alone does not automatically constitute disbelief**. *Istiḥlāl*—holding this recognized prohibition to be lawful—is a separate doctrinal case.
**Abū Muḥammad al-Juwaynī**, father of Imām al-Ḥaramayn, held the stricter view that deliberate lying about the Prophet entails *kufr*. His son, **Imām al-Ḥaramayn Abū al-Maʿālī al-Juwaynī**, rejected and weakened this view, calling it unrecognized among their colleagues and a grave lapse. Al-Nawawī endorses the majority's distinction. The gravity of the sin must neither be minimized nor turned into an unconditional charge of unbelief.