Questions on the Explanation of the Book of Nullifiers of Islam

Question:
There is a group who call themselves the Quranists. They say, "We do not act except on what is in the Qur'an." Do we declare them disbelievers?

Answer:
Yes, yes. There is no doubt about their disbelief, because they are lying when they say, "We do not act except on the Qur'an." The Qur'an commands us to follow the Messenger (peace and blessings be upon him), and following the Messenger includes acting on his Sunnah. Acting on his Sunnah is part of following the Messenger. Allah (Mighty and Majestic) says, "So follow him and obey the Messenger, so that you may be shown mercy" . It also says, "Obey the Messenger," and He says, "And what the Messenger gives you, take, and what he forbids you, abstain from" . The Qur'an contains matters that are summarized.
Only the Messenger (peace and blessings be upon him) explains them in his Sunnah. Take prayer, for example. Allah (Mighty and Majestic) mentioned prayer in the Qur'an and encouraged it, but did He specify for us the number of rak'ahs? The number of rak'ahs for the midday prayer, the afternoon prayer, the sunset prayer, the night prayer, and the dawn prayer? Who specified this for us?
Is there an explanation of this in the Qur'an? No. This is in the Sunnah of the Messenger (peace and blessings be upon him), and his saying, "Pray as you have seen me praying." Zakah is mentioned in the Qur'an, and there is a command to give zakah, but did the Qur'an specify the nisab (minimum threshold for zakah), the amount to be taken, and the types of wealth subject to zakah? The Messenger (peace and blessings be upon him) specified all of this. The Messenger (peace and blessings be upon him) specified all of this. So the Sunnah explains the Qur'an. Therefore, one who does not act on the Sunnah is not acting on the Qur'an. There are also matters not mentioned in the Qur'an that the Prophet (peace and blessings be upon him) brought and commanded us to act upon.
For example, his prohibition of marrying a woman and her maternal aunt together, or marrying a woman and her paternal aunt together. This was not mentioned in the Qur'an. Allah (Mighty and Majestic) said, "And [it is forbidden] that you take as wives your mother's sisters or your father's sisters" . The Messenger (peace and blessings be upon him) added in the Sunnah the prohibition of marrying a woman and her paternal aunt, or a woman and her maternal aunt.
So there are matters not mentioned in the Qur'an that were brought by the Sunnah of the Messenger, and we must act upon them just as we act upon the Qur'an. . The Prophet (peace and blessings be upon him), who does not speak from desire, referred to these people.
He referred to them by saying, "Soon there will be a well-fed man, leaning on his couch, saying, 'Between us and you is the Book of Allah; we will make lawful what it makes lawful and forbid what it forbids.'" Then he said (peace and blessings be upon him), The Prophet informed us about these people and warned us against them.