What is the best contextual account of fronting in lahu kufuwan aḥad?

Supplementary Practice 23: Comparative Rhetorical Study of Sūrat al-Masad and al-Ikhlāṣ

• All fronting makes a clause interrogative
• Fronting lahu makes aḥad accusative
• Fronting turns kufuwan into an imperative
• The relation is foregrounded, then equivalence and any possible equal are negated