Lam yaktubū is jussive by deletion of mood nūn, retaining the plural subject wāw. Lam yarmi is jussive by deletion of final weak yāʾ, leaving a kasra.
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Two Different Causes of Jussive Deletion
Choosing the Correct Parsing: Meaning, Governance and Context
Lam yaktubū is jussive by deletion of mood nūn, retaining the plural subject wāw. Lam yarmi is jussive by deletion of final weak yāʾ, leaving a kasra.