What is the meaning of the phrase "that the warning concerning belief indicates the prohibition of association by the implication of the discourse, and as for the claim of metaphor, the default is reality, and there is no recourse to deviating from it" which appears in Imam Al-Shawkani's book "Nayl Al-Awtar"?

Al-Shawkani summarizes the refutation of those who permit musical instruments by explaining that the word "they deem lawful" in the Hadith does not only imply verbal permissibility but also includes the actual prohibition of the act itself. Therefore, if Allah warns those who believe something to be permissible, this indicates, a fortiori (by implication of the discourse), the prohibition of the act itself. Al-Shawkani rejects interpreting the word figuratively as "indulgence in use," emphasizing that the original meaning of a word is its literal one unless there is evidence requiring deviation from it.