The Power of Keeping the Precepts

Formerly, in Kubhana state (Kashmir), there was nearby a monastery a poisonous dragon which frequently played havoc in the region.
In the monastery five hundred arhats gathered together but failed to drive away the dragon with their collective power of Dhyana-samadhi. Later, a monk came to the monastery where he did not enter into Dhyana-samadhi; he merely said to the poisonous dragon: 'Will the wise and virtuous one leave this place and go to some distant one.' Thereupon, the poisonous dragon fled to a distant place.
When asked by the arhats what miraculous power he had used to drive away the dragon, the monk replied: 'I did not use the power of Dhyana-samadhi; I am only very careful about keeping the rules of discipline and I observe a minor one with the same care as a major one.'
So, we can see that the collective power of five hundred arhats' Dhyana--samadhi cannot compare with a monk's strict observance of the rules of discipline.