Why is faṣl used in «ارْحَلْ لَا تُقِيمَنَّ عِنْدَنَا» despite differing forms?

Faṣl: Substitution, Quasi-Complete Connection and Quasi-Complete Disjunction

• The second has no subject
• It always expresses reversal restriction
• Both pursue the same practical end, with the second reinforcing the first
• Commands and prohibitions can never be related