Three questions help analyze a prohibitive-looking expression.
1. Form: Is lā prohibitive, governing a jussive imperfect?
2. Situation: What is the relationship between speaker and addressee? Can the addressee control the requested action?
3. Contextual indication: Is the expression really forbidding, imploring, requesting, wishing, or threatening?
Example: “Yā ṣubḥu lā taṭluʿ” — prohibitive syntax, dawn as addressee, impossible literal enforcement; therefore a wish.
Example: “Lā tabraḥ ḥattā arjiʿ” — prohibitive form; iltimās if the participants are peers, but potentially a literal ban if spoken by an authorized superior.