«فَمَن شَاءَ فَلْيُؤْمِن وَمَن شَاءَ فَلْيَكْفُرْ»
Let whoever wills believe, and whoever wills disbelieve.
Both verbs employ an imperative form. Yet the verse does not establish that disbelief is approved or religiously permitted. Given who speaks and the nature of the address, the formulation functions as warning and threat, not a legal authorization to reject faith.
فلا يكون للإيجاب
The form is not read as making unbelief obligatory or approved.
A grammatical imperative may express command, permission, warning, challenge, or another communicative force. The intended force must be grounded in the speaker and the surrounding indications.
Failing to distinguish form from function would yield an interpretation contrary to the established nature of the address.