In one report Ali told a judge who had no knowledge of nasikh that he was "deluded and misleading others", in another he evicted a preacher from a mosque for being ignorant of the science of abrogation. Umar is reported to have told Muslims that despite the fact that Ubay ibn Ka'b was "the best Quranic expert among us ... we ignore some of what" he says because he disregarded abrogation and told others he refused to "abandon anything I heard from the Messenger of Allah".