What is the central function of the final “illā alladhīna āmanū wa-ʿamilū al-ṣāliḥāt”?

Supplementary Practice 29 — Comparative Rhetoric of Sūrat al-Infiṭār and Sūrat al-Inshiqāq

• Deprecation through a demonstrative
• The same punishment without exception
• Exception setting apart the believers’ destiny
• A temporal limit imposed by an oath