Praise be to Allah, and peace and blessings be upon the Messenger of Allah. To proceed:
A Jew or Christian does not become a Muslim merely by believing in Allah Almighty and affirming His Oneness, or by acknowledging the Messengers and Books, while refusing to accept the Qur’an as the authority and follow the law of the Prophet Muhammad ﷺ. Rather, he must believe in the Prophet Muhammad ﷺ, follow his law, and accept the Qur’an as the authority, because the Muhammadan message is the final message and abrogates the laws that preceded it.
One of the foundations of faith is that a Muslim believes in all the Books that Allah Almighty revealed and in all His Messengers, peace be upon them. This includes believing in the Noble Qur’an and in the Prophet Muhammad ﷺ, the Seal of the Prophets and Messengers and the Messenger of Allah to all people.
Whoever receives the message of the Prophet Muhammad ﷺ must believe in him, follow him, and accept his law as the authority. It is not sufficient to acknowledge that the Qur’an is from Allah and then refuse to abide by what it brought.
Belief in a Messenger is not merely knowledge or intellectual acknowledgment; rather, it includes affirmation, submission, following, and accepting his judgment.
The scholars have explained that merely believing in the truthfulness of the Prophet ﷺ is not sufficient while persisting in refusing to follow him. Some of the polytheists knew that the Prophet ﷺ was truthful; indeed, some acknowledged his truthfulness inwardly or verbally. Nevertheless, this acknowledgment did not benefit them because they refused to follow the Messenger ﷺ.
Likewise, the People of the Book knew the Prophet ﷺ and found his description in what they knew from their Scriptures. However, knowledge of the truth alone did not benefit those who refused to believe in him and follow him.
Allah Almighty says:
﴿He is the One Who sent His Messenger with guidance and the religion of truth to make it prevail over every religion, even though the disbelievers dislike it.﴾ [At-Tawbah: 33].
No. After the Prophet Muhammad ﷺ was sent, his law became obligatory for all people to follow, and the Noble Qur’an became the authoritative guardian over the previous Books.
Allah Almighty says:
﴿Whoever seeks a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers.﴾ [Aal ‘Imran: 85].
Therefore, it is not valid for someone to say: “I believe that the Qur’an is from Allah, but I choose to follow the original Torah instead of the law of Islam.” Belief in the Qur’an entails accepting what it brought, and belief in the message of Muhammad ﷺ entails following him.
The Muhammadan message is the final message, and it abrogated the laws that preceded it. Therefore, after the Prophet ﷺ was sent, it is not valid to adhere to a previous religion while refusing to follow him.
The Prophet ﷺ said:
“By Him in Whose Hand is the soul of Muhammad, no one from this community—whether Jew or Christian—hears of me and then dies without believing in what I was sent with, except that he will be among the inhabitants of the Fire.” Narrated by Muslim (153), and in the source under number (218).
This indicates the obligation to believe in the Prophet ﷺ and follow what he brought for whoever receives his message.
Believing in Allah Almighty and affirming His Oneness, and believing in the Messengers and Books, is not sufficient by itself after the Prophet Muhammad ﷺ was sent for whoever has received his message. Rather, it is necessary to believe in him ﷺ, affirm his truthfulness, follow his law, and accept the Noble Qur’an as the authority.
The Qur’an is the authoritative guardian over the previous Books, and Islamic law is the law that must be followed after the Prophet Muhammad ﷺ was sent. It is not valid to adhere to a previous law while refusing to follow the Muhammadan message.
And Allah knows best.