Why can “rabbi innī wahana al-ʿaẓmu minnī” be rhetorically effective despite its length?

Ījāz, Iṭnāb and Musāwāt: Standards of Expression and Their Distinctions

• It explicitly states a numerical age
• It equals customary wording exactly
• Its effect lies only in sound and rhyme
• It vividly conveys aging and weakness