What is the dominant rhetorical purpose of “mā gharraka bi-rabbika al-karīm”?

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

• A neutral inquiry into an unknown cause
• An oath about a future event
• Restricting who deserves reward
• Rebuking negligence by recalling divine favor