The figure establishes closure and recall: the ending sends the listener back to an earlier expression and gives the passage a more memorable shape.
Istaghfirū/ghaffārā links petition and promise; sarīʿ/sarīʿ intensifies a judgment of character; ḍāʾirī/yaḍīr belittles a threat.
Yet forced verbal similarity can injure the meaning. Successful embellishment supports the rhetorical intention rather than overriding it.