وَالصِّلَةُ جُمْلَةٌ خَبَرِيَّةٌ.
Translation: The relative clause is declarative.
A declarative clause states something: «الَّذِي كَتَبَ الدَّرْسَ» — the one who wrote the lesson.
A bare imperative like «الَّذِي اُكْتُبْ» is not a valid ṣilah on this ordinary analysis.
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Relative Nouns — Ṣilah, ʿĀʾid, Forms and Syntax
وَالصِّلَةُ جُمْلَةٌ خَبَرِيَّةٌ.
Translation: The relative clause is declarative.
A declarative clause states something: «الَّذِي كَتَبَ الدَّرْسَ» — the one who wrote the lesson.
A bare imperative like «الَّذِي اُكْتُبْ» is not a valid ṣilah on this ordinary analysis.