Command and Prohibition: One Important Difference

The Prohibitive Verb (Fi'l Nahi) - Concept & Construction

In an active addressed command, the Mudhaari' prefix is removed. In prohibition, the Mudhaari' form keeps its prefix and takes prohibitive Laa.

ResultMeaningType
اِضْرِبْHit!Command
لَا تَضْرِبْDo not hit!Prohibition

So the addressed prohibition keeps the initial Mudhaari' marker.