«وَإِنْ أَسْهَبَ أَذْهَبَ»
When he speaks at length, he carries his audience away.
Ashaba means to expand or speak at length. The paired adhhaba suggests taking something away or carrying it to a further effect. The elder uses the sound parallel to praise unusually engaging extended speech.
The claim is not that length is inherently excellent. Proper expansion works when detail is needed and retains the listener’s attention. Concision and elaboration are both possible instruments of eloquence, depending on purpose.