Why combine “better” and “more lasting” about the Hereafter?

Supplementary Practice 28 — Comparative Rhetoric of Sūrat al-Aʿlā and Sūrat al-Ghāshiyah

• Khayr denotes only duration and abqā denotes only value
• Together they create the response to an oath
• Each adjective entirely negates the other
• To combine distinct criteria of superiority and permanence