إِنْ رَأَيْتَ خَطَأً فَلَا تُكَرِّرْهُ.
Translation: If you see an error, do not repeat it.
The fāʾ links a prohibition to the condition. Prohibitive lā, not fāʾ, governs tukarrir in the jussive.
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A Prohibition as the Response
The Jussive Imperfect: Governors, Conditions, and Request Responses
إِنْ رَأَيْتَ خَطَأً فَلَا تُكَرِّرْهُ.
Translation: If you see an error, do not repeat it.
The fāʾ links a prohibition to the condition. Prohibitive lā, not fāʾ, governs tukarrir in the jussive.