جَاءَ كِلَاهُمَا.
Translation: Both of them came. Here كِلَاهُمَا is nominative with alif because هُمَا is a pronoun.
جَاءَ كِلَا الرَّجُلَيْنِ.
Translation: Both men came. Here كِلَا is annexed to the visible noun «الرَّجُلَيْنِ». Its nominative case is estimated on the final alif; that alif is not a nominative case sign.
Crucial: The first example meets the book’s explicit condition; the second is an added grammatical contrast.
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Noun Case Classes: Type 5 — The Dual and Related Forms
جَاءَ كِلَاهُمَا.
Translation: Both of them came. Here كِلَاهُمَا is nominative with alif because هُمَا is a pronoun.
جَاءَ كِلَا الرَّجُلَيْنِ.
Translation: Both men came. Here كِلَا is annexed to the visible noun «الرَّجُلَيْنِ». Its nominative case is estimated on the final alif; that alif is not a nominative case sign.
Crucial: The first example meets the book’s explicit condition; the second is an added grammatical contrast.