Does the Hadith, "He will be released from the Fire, whoever said 'La ilaha illa Allah' and had in his heart goodness weighing a barley-corn...", include the People of the Book who affirm the oneness of God but do not believe in Muhammad (peace be upon him)? And what is the ruling regarding those who do not declare the People of the Book to be disbelievers?

The Holy Qur'an explicitly states the disbelief (kufr) of the People of the Book who did not believe in Prophet Muhammad (peace be upon him), or associated partners with Allah, or denied the prophethood of any of the prophets. This is supported by Allah's saying: "Indeed, those who disbelieve in Allah and His messengers and wish to discriminate between Allah and His messengers and say, 'We believe in some and disbelieve in others,' and wish to adopt a way in between - Those are truly disbelievers. And We have prepared for the disbelievers a humiliating punishment." {An-Nisa: 150-151}.

Therefore, true monotheists are those who believe in Allah alone, and believe in Muhammad (peace be upon him) and all that he brought, adhering to his law. This can only be achieved through Islam. Allah Almighty said: "Indeed, the religion in the sight of Allah is Islam." {Al Imran: 19}. And He said: "And whoever seeks a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers." {Al Imran: 85}.

The Jews and Christians are polytheists and deny the prophethood of Muhammad (peace be upon him), and Islam has abrogated the previous laws. Whoever does not believe in Muhammad (peace be upon him) after his message has reached them, is a disbeliever abiding eternally in Hellfire if they die upon that, as the Prophet (peace be upon him) said: "By the One in Whose hand is my soul, no one from this nation, neither a Jew nor a Christian, hears of me, and then dies without believing in that with which I was sent, except that he will be among the people of the Hellfire." Narrated by Muslim. And his saying: "None will enter Paradise except a Muslim soul." Agreed upon.

The disbelief of the People of the Book is affirmed by text (Qur'an and Sunnah) and scholarly consensus (Ijma'), and is known to be an essential principle of the religion. Whoever does not consider them disbelievers is himself a disbeliever, unless they are ignorant, or misinterpret, or have a misconception, in which case proof must be established against them before declaring them disbelievers.