Calling “book” unrestricted does not mean it must not be Arabic. Both Arabic and non-Arabic books can fall under the word; Arabic was simply not made a condition.
Likewise, failure to specify mu’minah does not turn the expression raqabah into a requirement for a non-believer. Silence about an attribute is not affirmation of its opposite.
Remember: absence of a qualification differs from a stated exclusion; an explicit qualification positively limits what is required.
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Mutlaq and Muqayyad: Definitions, Qur’anic Examples and Legal Effect
Calling “book” unrestricted does not mean it must not be Arabic. Both Arabic and non-Arabic books can fall under the word; Arabic was simply not made a condition.
Likewise, failure to specify mu’minah does not turn the expression raqabah into a requirement for a non-believer. Silence about an attribute is not affirmation of its opposite.
Remember: absence of a qualification differs from a stated exclusion; an explicit qualification positively limits what is required.