48:13Al-Fath

By Him in Whose hand is the life of Muhammad, he who amongst the community of Jews or Christians hears about me, but does not affirm his belief in that with which I have been sent and dies in this state (of disbelief), he shall be but one of the denizens of Hell-Fire.

that the Messenger of Allah (ﷺ) said: "Whoever lies upon me, then let him take his seat in the Fire."

that the Messenger of Allah (ﷺ) said: "Whoever says (something) about the Qur'an without knowledge, then let him take his seat in the Fire."

We witnessed along with Allah's Messenger (ﷺ) the Khaibar (campaign). Allah's Messenger (ﷺ) told his companions about a man who claimed to be a Muslim, "This man is from the people of the Fire." When the battle started, the man fought very bravely and received a great number of wounds and got crippled. On that, a man from among the companions of the Prophet (ﷺ) came and said, "O Allah's Apostle! Do you know what the man you described as of the people of the Fire has done? He has fought very bravely for Allah's Cause and he has received many wounds." The Prophet (ﷺ) said, "But he is indeed one of the people of the Fire." Some of the Muslims were about to have some doubt about that statement. So while the man was in that state, the pain caused by the wounds troubled him so much that he put his hand into his quiver and took out an arrow and committed suicide with it. Off went some men from among the Muslims to Allah's Messenger (ﷺ) and said, "O Allah's Messenger (ﷺ)! Allah has made your statement true. So-and-so has committed suicide." Allah's Messenger (ﷺ) said, "O Bilal! Get up and announce in public: None will enter Paradise but a believer, and Allah may support this religion (Islam) with a wicked man."

The Prophet (ﷺ) said, "By Allah, he does not believe! By Allah, he does not believe! By Allah, he does not believe!" It was said, "Who is that, O Allah's Messenger (ﷺ)?" He said, "That person whose neighbor does not feel safe from his evil."