«والإنشاء: ما لا يصح أن يقال لقائله ذلك»
Inshāʾ is speech concerning which the speaker is not characterized as truthful or false in the same sense.
“سَافِرْ يَا مُحَمَّدُ”
“O Muhammad, travel!”
The speaker is issuing a command rather than reporting a journey. The command may be obeyed or disobeyed, but the command itself is not a true or false statement of fact.
Likewise, “هَلْ سَافَرَ مُحَمَّدٌ؟” asks whether Muhammad travelled; it does not assert that the journey occurred.