In governs the mood of conditional imperfect verbs, not the case of a subject noun. Yaktub and yafham are jussive; Zayd is nominative.
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Jussive Case after In
Conditional Particles: In, Law and Ammā
In governs the mood of conditional imperfect verbs, not the case of a subject noun. Yaktub and yafham are jussive; Zayd is nominative.