How can one reconcile the threat of hellfire for the parents of the Prophet (PBUH) because of their demise in the pre-Islamic era (Jahiliyyah) before Islam reached them, with the principle that authentic hadiths are not 100% definitively proven and can be challenged with a legitimate Sharia-compliant justification? And does denying a hadith that appears to contradict Islam make its denier an infidel?

We have previously discussed the hadith of the female infanticide (al-Wa'idah), and that the hadith is specific to the infanticide and the buried female infant mentioned therein, and is not general.

The principle is to prevent the rejection of a hadith after its authenticity has been established. Whoever rejects it without a valid proof, there is a fear of falling into disbelief for them.

Ishaq ibn Rahawayh said: "Whoever receives a report from the Messenger of Allah, peace and blessings be upon him, and acknowledges its authenticity, then rejects it without dissimulation (taqiyyah), is a disbeliever."

Al-Suyuti said: "Whoever denies a hadith of the Prophet, peace and blessings be upon him, be it a saying or an action, with its known conditions for being a proof in Usul (principles of Islamic jurisprudence), has disbelieved and exited the fold of Islam."

Ibn al-Wazir said: "Indeed, the denial of a hadith of the Messenger of Allah, peace and blessings be upon him, while knowing it is his hadith, is clear disbelief."

However, one does not commit an act of disbelief by rejecting the authoritativeness of a hadith that they believe contradicts the texts of the Quran or the mutawatir (globally transmitted) Sunnah. Nevertheless, one should maintain respect for the Sunnah, diligently research the authenticity of the hadith, reconcile it with what seems to contradict it, and measure oneself against the scholars and companions, recognizing that there is a significant difference.