Is the one who claims to be a Muslim, but associates partners with Allah, and the argument has not been established against him, is he truly a Muslim?

Question:
May Allah reward you, Honorable Shaykh. The questioner asks: Is the one who claims to be a Muslim, but associates partners with Allah, and the argument has not been established against him, is he truly a Muslim?

Answer:
Why was the argument not established against him? After the sending of the Messenger (peace and blessings be upon him), the argument was established. Every Muslim who reads the Qur'an or hears the Qur'an, the Qur'an is the argument. He (Exalted and Majestic is He) said: "And We have revealed to you the reminder" . Whoever the Qur'an has reached, the argument has been established against him. One is only excused by ignorance if he grew up in a place far from Muslims where he did not hear the Qur'an or any news about Islam. This is the one who is excused until it is made clear to him. As for the one who grew up in the lands of Muslims and heard the Qur'an and read the Qur'an, the argument has been established against him.