Commands and prohibitions can acquire additional emphasis through heavy or light nūn. This strengthens the directive or prohibition without changing the root.
Word / formMeaning / explanation
خَفْfear!
لَتَخَافَنَّyou will certainly fear (emphatic assertion).
لَا تَخَافَنَّdo not fear at all (emphatic prohibition).
لَا تَخَافَنْa light-nūn emphatic prohibition.
Distinguishing the emphatic nūn from the role of lām or lā prevents confusion between an emphatic statement and an emphatic prohibition.