Not every jussive verb ends in a newly added sukūn. With a weak-final verb (nāqiṣ), jussive formation can remove the final weak letter. Identify the correct imperfect stem and weak root before applying the prohibition rule.
Word / formMeaning / explanation
يَدْعُو → لَا يَدْعُlet him not call.
يَرْمِي → لَا يَرْمِlet him not throw.
يَسْعَى → لَا يَسْعَlet him not strive.
Deletion of a weak final letter is a different jussive marker from deletion of an inflectional nūn. These examples extend the basic source rule to weak-final verbs.