The two clauses employ different forms: «ارْحَلْ» is an imperative, whereas «لَا تُقِيمَنَّ» is a prohibition. Yet both pursue the same communicative goal: the addressee is not to stay. Their semantic unity may therefore outweigh the difference in grammatical form.
ExpressionGrammatical/rhetorical value
ارْحَلْImperative: a demand to depart
لَا تُقِيمَنَّProhibitive lā with emphatic nūn: strong bar on remaining
No wāw between themAllows the second expression to emphasize or explain the first
The relation of meaning and the speaker’s intention, not grammatical form alone, decide the rhetorical classification.