«وَسَحَبُوا عَلَى سَحْبَانَ ذَيْلَ النِّسْيَانِ»
They seemed to draw the hem of forgetfulness over Saḥbān.
Saḥbān alludes to a celebrated orator. A dhayl is a trailing hem; drawing it over someone creates an image of covering or obscuring them.
The narrator praises the companions so extravagantly that a famously eloquent speaker seems forgotten. It is literary hyperbole, not a factual claim about a historical contest.