How can one respond to someone who cites the poetic verse "You are the one named in the Qur'an" to prove the existence of the Qur'an before the Prophet Muhammad, peace be upon him, knowing that there is another narration of the verse with the wording "al-Furqan"?

One should be cautious about accepting everything found in history and سیرت (prophetic biography) books, as many of them are filled with falsehoods. It is crucial to distinguish between what is authentic and what is not, especially concerning matters that imply a religious ruling. Islamic history is distinguished by the methodology of isnad (chain of narration) to differentiate the authentic from the weak.

Regarding the narration attributed to Abd al-Muttalib that mentions "al-Furqan" or "al-Qur'an": 1. The incident is narrated without an isnad from Muhammad ibn Ishaq, rendering it unacceptable. 2. The original wording in Ibn Ishaq's narration is "al-Furqan," which encompasses previous scriptures like the Torah. This is indicated by its description as being "in well-established books of oft-repeated verses," and the fact that the Qur'an did not exist by this name during Abd al-Muttalib's time. 3. Even if the verses were authentic and the word "al-Qur'an" appeared in them, it would refer to a read book in general. It could also refer to the Torah or the Psalms, as the Psalms were referred to as "Qur'an" in the Sunnah. 4. The narration stating that Abd al-Muttalib named his grandson "Muhammad" so that he would be praised in the heavens and on earth is closer to reality. It is not because he found his name in previous scriptures, which contradicts the questions: Why did none of his other sons bear that name? And why did his people fight the Prophet despite knowing him?